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Deciduous Wetland FLats Interim HGM Model

Deciduous Wetland Flats Interim HGM Model

CONTENTS

Deciduous Wetland Flats Interim Hydrogeomorphic Model

Southeast Forested Depressional Wetlands Hydrogeomorphic Method

Deciduous Wetland Flats Model

Southeast Forested Depressional Model


Deciduous Wetland Flats Interim Hydrogeomorphic Model

 Initial Model Format by Dr. Rick Rheinhardt and Dr. Mark Brinson

Modified & Compiled by N. Eric Fleming, and J. Glenn Sandifer, Jr.

Workgroup: Matt Flint, NRCS NC; Larry Hobbs, NC DWQ; Anita Goetz, USFWS NC; Kevin Moody USFWS NC; John Gagnon, NRCS NC; Ken Jolly, USACE Wilmington District; David Lekson, USACE Wilmington District; Greg Moser, NRCS VA; Jerry Quesenberry, NRCS VA; John Nicholson, NRCS VA; Sharon Boone, NRCS VA; Jeannine Freyman, NRCS VA; Jennifer McCarthy, USACE Norfolk District; and Leander Brown, NRCS WLI

 Preface

This document was prepared for use in the coastal plain of southern Virginia and northern North Carolina. The NRCS Major Land Resource Areas which encompass the area are 153, 133A, and 137 (USDA 1981). The format and many of the variables rely heavily upon the preliminary work done by Dr. Rick Rheinhardt and Dr. Mark Brinson at the request of the NRCS SE Coastal States Wetland Team. The preliminary model was developed by combining material from Dr. Rheinhardt’s Mineral Flats HGM model (under development) and the existing knowledge of deciduous forested systems.

The preliminary model was presented to a multistate, multiagency, multidisciplinary work-group composed of NRCS, USACE, USFWS, and NC DWQ personnel from Virginia and North Carolina at a session in Elizabeth City, NC the week of October 6, 1997. The group commented on the use of the model structure, the proposed functions, and its variables. The variable scaling is currently a combination of the original estimates from the preliminary model and best guesses to be refined as the model is used and as data is collected. The NRCS Southeast Coastal States Wetlands Team agreed to modify the existing model and incorporate the comments of the interagency group to create a deciduous wetland flats interim HGM model. The intent of this effort is to create an interim HGM model for NRCS’s use under the 1996 Farm Bill (the Federal Agriculture Improvement and Reform Act of 1996, FAIRA) which can later be tied to reference sites and developed into a full HGM model. This process was used to meet NRCS’s requirements of having procedures in place to meet the new wetland flexibility provisions of the Farm Bill while still generating a product which can be better defined in the future for more rigorous applications.

The draft deciduous wetland flats model is to be forwarded to the workgroup participants for comments. After comments are incorporated, the intent is to field test the resulting interim model. The process of field testing will allow data collection to begin as well as the selection of reference sites for model scaling.

 Wetlands of North Carolina and Virginia

Wetlands in North Carolina

About 5.7 million acres of North Carolina - 17 percent of the State - is wetland. The Coastal Plain contains 95 percent of the State’s wetlands. Before colonization by Europeans, North Carolina had about 11 million acres of wetlands. Nearly one-third of the wetland alterations in the Coastal Plain have occurred since the 1950’s; most have resulted from conversion to managed forests and agriculture. The Roanoke River flood plain has one of the largest intact and least disturbed bottom-land hardwood forests in the Mid-Atlantic region. About 70 percent of the rare and endangered plants and animals in the State are wetland dependent. (Fretwell et al. 1996)

 

Wetlands in Virginia

Virginia has about 1 million acres of wetlands; one-quarter are tidal and three-quarters are nontidal. Forested wetlands (swamps) are the most common wetlands in the State. Both shores of the Chesapeake Bay have extensive estuarine wetlands. Conversion to nonwetland uses (agricultural, urban, industrial, and recreational), channelization and ditching, and other causes have resulted in the loss of about 42 percent of Virginia’s wetlands since the 1780’s. Development in wetlands is regulated in part by means of the Virginia Water Protection Permit. Local governments may adopt prescribed zoning ordinances and form citizen wetland boards to regulate their own tidal wetlands; the State retains an oversight and appellate role. (Fretwell et al. 1996)

 

Deciduous Mineral Flats

Deciduous mineral flats were described at the work session as follows. The HGM class is flats. The subclass is mineral soils, with by deciduous vegetation. The trees are primarily deciduous hardwoods, but some pines can be present. The expected location of these wetlands is the coastal plain of Virginia and northern North Carolina. These wetlands are not fire maintained, which is a major distinction from the pine dominated mineral flats found further south on the coastal plain. These wetlands are primarily precipitation driven, have no drainage patterns present, and are seasonally saturated. They can be described as large, broad flats of the coastal plain dominated by deciduous vegetation.

 Functional Profile

Maintenance of Characteristic Hydrologic Regime

Definition: The conditions in a wet flat that affect the fluctuation in water level, including variations in depth, duration, frequency, and season of ponding. The on-site effects are sustaining conditions favorable for biogeochemical processes that require anoxic conditions and maintenance of wetland vegetation. The off-site effects are maintenance of regional water quality and acts as a source area for stormflow.

Discussion and Rational: This function was recognized as a composite of specific sub-functions during the work session. The sub-functions are long term surface water storage, subsurface storage of surface water, and moderation of off-site groundwater flow. The approach taken was to look at potential impacts to the wetland hydrology, such as the presence to drains, or the absence of vegetation which would change the characteristic evapotranspiration.

Variable Descriptions:

Presence of a Constructed Drain (Vdrain)

This variable addresses the presence of a constructed drain which will remove the surface and groundwater from the site. The drain would typically be a constructed ditch, but could be a subsurface tile line, or something which functions as a drain such as deep ruts in a logging road. One important factor for this variable is whether an effective outlet is present. The lack of an outlet can cause the drain to be negligible. A series of tables has been developed, based upon the expected soil series in NC and VA which will occur on the deciduous flats and the size of the ditch. The distances in the tables have been calculated using the Van Schilfgaarde equation (USDA 1997). The concept of the variable is that a ditch with a free outlet will remove the wetland hydrology a given distance from it (zone 1) and that the wetland hydrology is impacted to another, further out line (zone 2). Beyond the second line, the hydrology of the wetland is assumed to be unaffected. The areas of each zone (which occur in the wetland assessment area) are calculated and multiplied by the weighting factor. The total is then divided by the wetland assessment area to determine the variable score. See Appendix A for the lists to determine the zonation and Figure 1 showing the zonation.

Zone Zone Score

1 0.1

2 0.5

3 1.0

Vdrain = [ (Area Zone1 X 0.1) + (Area Zone2 X 0.5) + (Area Zone3 X 1)] / AreaTotal

Note: This procedure is invalid for use in wetland delineations. The calculations were performed with the intent of showing relative differences for HGM assessment purposes -- not to determine the wetland line as affected by drainage.

Presence of Impediments to Surface Flow (Vdam)

This variable accounts for the presence of impediments to overland flow within the watershed. The landscape position of the wetland flats does not allow rapid, channelized flow of water from the site. However, there are gradual gradients which cause slow, shallow flow to occur in a general direction. This variable is intended to show the effect of a fill which would disrupt the gradual flow. This could be the presence of a road fill which causes damming - water ponded deeper and longer on the upstream side, and a shallower and shorter hydroperiod on the downstream side of the fill. The method of evaluating this variable is to determine the height of the impediment and the upstream area (within the wetland assessment area) impounded. The downstream area is estimated by using the same size area as the upstream area. The area of the impediment itself is also determined. A weighted average is then determined for the variable score. See Appendix A for Figure 2 showing the areas.

Area Area Score for Formula

1 -- unaffected by impediment 1.0

2 -- area upstream of impediment 0.1

3 -- area of impediment 0.0

4 -- area downstream of impediment 0.3

Vdam = [(Area1 X 1.0) + (Area2 X 0.1) + (Area3 X 0) + (Area4 X 0.3)] / AreaTotal

One situation which can complicate the determination of the Vdam is the case where a fill occurs, such as a road, and a ditch is present also. The procedure for this situation should be to evaluate both the impediment and the drain independently and the procedure for determining the FCIhydro will sort out the dominant effect.

 Evapotranspiration (Vet)

This variable represents the characteristic evapotranspiration (ET) potential of the wet deciduous flat. To some extent, the evaporation and transpiration factors are offsetting. For densely vegetated sites, most of the ET is in the form of transpiration because of the limited free water surface for evaporation. For nonvegetated sites, the ET will be entirely evaporation and no transpiration will occur. However, as this phenomenon relies upon an open water surface from which water can evaporate, and these wetlands are seasonally saturated rather than long duration ponding (and if open water is present on the surface, it should be covered by vegetation in a reference standard site), the presence of vegetation should "pump" water out of the soil profile as transpiration. The general unimportance of vegetation-species variation on overall wetland water loss is probably a reasonable conclusion for most wetlands, although it is clear that the type of wetland ecosystem and the season are important considerations (Mitsch and Gosselink 1993). Because of this, it follows that it is the presence and amount of vegetation which is critical, rather than the specific type of vegetation. Intuitively, in a forested system, trees will be able to remove water from deeper in the soil profile because of a more extensive root system. If the trees are removed, the system will stay saturated longer and the saturation will be higher in the profile.

Cover Condition Variable Index

Relatively mature stands of vegetation (5yrs +) 1.0

Agricultural use (crops or pasture) 0.3

Recent clear cut (less than 5yrs) 0.1

Impervious surface 0.0

Soil Quality (Vsoilq)

This variable represents the physical integrity of the soil above the Bg or Btg horizon. This includes the number and continuity of pores and the type, grade, and size of soil structure. Measurement of soil condition will involve looking at roots, pores (abundance, size, and continuity), and soil friability (rupture resistance, from very friable to very friable and harder. Measurement is done on the more limiting part of the A horizon, directly above the Bg or Btg horizon. The Soil Quality Index (SQI) will be assigned for each of the three measured soil parameters. The points for each soil parameter will then be added. The Vsoilq index will be assigned based upon the total for the three soil parameters.

Pores: The quality and continuity of soil pores received a quantitative score of 1 through 3. Many fine and very fine pores in the A horizon receive a score of 3. Common pores receive a score of 2, and few pores a score of 1. Any deviation from the standard may be an indication that the site is not functioning to full capacity hydrologically. Less evidence of macropores indicates less water moving downward through the soil profile to recharge the water table. Nonmatrix and interstructural porosity have particular importance for water movement.

Consistence (Moisture): Consistence is now called "Rupture Resistance Classes for Block-like Specimens, slightly dry and wetter." Very friable and friable rupture resistance in the A horizon was indicated by a score of 3. Firm was indicated by a score of 2, and very firm or harder by a score of 1. This measure is an indication of compaction, which increases bulk density, which in turn reduces porosity.

Structure: Soil structure was rated according to the following metrics. Structure that was "Weak or moderate subangular blocky parting to moderate fine and medium subangular blocky parting to fine and medium granular" in the A horizon was noted by a score of 3. Fine to medium subangular blocky parting to granulate in the A horizon was scored as a 2. Massive or coarse subangular blocky or evidence of a plowpan were designated as a 1. A plowpan was indicated in the field by dense coarse, or massive, structure, and roots growing horizontally across the top of the pan.

Soil Quality Index Score Variable Index

greater than or equal to 7 1.0

4 - 6 0.5

less than or equal to 3 0.1

substrate is concrete, or non-porous 0.0

Material for this variable was provided by Leander Brown, NRCS Wetland Science Institute.

 Changes in Wetland Storage Volume (Vvol)

This variable represents the change in surface water storage capacity of a wet flat in response to removal or addition of material. The rational for including this variable is that changes in the surface storage capacity affects the water level of the wet flat. The storage capacity varies with the depth of ponding which can occur. However, the depth of ponding tends to be relatively shallow in wet flats and any fills which occur are likely to be designed to bring the land surface above the depth of normal ponding. So, an assumption can be made that the height of fill is equal to or greater than the normal depth of ponding and that the changes in wetland storage volume depends much more on the area of fill rather than the depth of fill. The other condition which could occur is an excavated area within the wetland assessment area. This effect can also be dealt with in a similar manner as the fill case. Any excavation is likely to be to the greatest depth of the water table (such as for livestock watering ponds). The excavated area will cause some drawdown effect to occur, but it will be limited due to the lack of an outlet. In this situation, the volume of the excavation which must be addressed is only the actual volume of soil particles removed, because the pore volume would be taken up by water anyway. So, once again the surface area of the excavation is the primary factor.

Variable Index

Areas which have been filled or excavated score 0.0.

Vvol = [1.0 - (Area of impact / Area of wetland assessment site)]

 Index of Function

FCIhydro = minimum of [ (Vet + Vsoilq) / 2 or Vdrain or Vdam or Vvol]

 Maintenance of Characteristic Biogeochemical Transformations

Definition: The capacity of a wet flat to maintain biological, chemical and physical processes which cycle compounds from one form into another. The on site effects are maintaining the availability of nutrients for the living components of the system and maintaining the characteristic level of decomposition of the dead component. This function can be quantified in tons/acre/year of nutrients and compounds as the basic mass balance of the wetland.

Discussion and Rational: This function was recognized as a composite of specific sub-functions during the work session. The specific sub-functions are biogeochemical transformations and processing, and storage of soil organic carbon.

Phosphorus, nitrogen, carbon, and other elements are found in various forms in the water, soil, plants, microbes, animals, detritus, etc. These elements are in a constant state of flux as they cycle from one form to another. The function has been structured to account for the major components of this system. Variables have been included to account for the living component of the system, the dead component of the system, the hydrology of the system, and the soil of the system.

Variable Descriptions:

Biomass of Hardwood Canopy (Vba)

This variable is a surrogate for the amount of nutrients and compounds held in the tree layer, the amount of nutrients and compounds the tree layer takes up, and the nutrient cycling which occurs at any oxidized rhizospheres around the tree roots. For the purposes of this variable, only hardwood canopy trees should be considered. The trees considered are only those greater than 6 in (15 cm) dbh. This variable provides an indication of the forest maturity and living forest biomass.

Hardwood Basal Area Variable Index

greater than 125 ft2/ac 1.0

100 - 125 0.7

75 - 99 0.3

less than 75 0.1

Not restorable 0.0

 Biomass of Standing Dead Trees (Vsnag4)

This variable represents the biomass of standing dead trees greater than 4 inches in diameter and greater than 15 ft tall. Standing dead trees is one component of detrital biomass available for nutrient cycling. This variable is measured by using the point-center-quarter method (Brookhout 1996). A point is established in the center of the wetland assessment area / sampling area and quarters are established by setting up perpendicular lines crossing at the center point. The distance to the closest snag (meeting the above size criteria) is measured, if within 225 ft., in each quarter. If the distance is greater than 225 ft., or no snag is visible in that quarter, use 225 ft. So, four measures should be made, one for each quarter of the circle and an average distance is calculated. The average distance is used in the following formula to determine the density of 4 in diameter snags.

Density of 4 in. Snags = 43560 / (avg. distance)2

4 in. Snags/Acre Variable Index

greater than 19 1.0

12 - 18 0.5

5 - 11 0.2

less than 5 0.1

site converted 0.0

 Biomass of Coarse Woody Debris (Vcwd)

This variable represents the accumulation of dead woody material which is available for nutrient cycling. For the purposes of this variable, the debris must be 4 inches or greater in diameter, and over 3 feet long to count. This variable is to be measured using a modified version of the point-center-quarter method. A point is established in the center of the wetland assessment area / sampling area and quarters are established by setting up perpendicular lines crossing at the center point. The distance to the closest coarse woody debris (meeting the above size criteria) is measured, if within 225 ft., in each quarter. If the distance is greater than 225 ft., or no coarse woody debris is visible in that quarter, use 225 ft. So, four measures should be made, one for each quarter of the circle and an average distance is calculated. The average distance is used in the following formula to determine the density of coarse woody debris.

CWD = 15175 / (average distance)2

The numerator (15175) in the above equation is a factor to convert the density version of the point-center-quarter method into a volumetric term. Using this factor assumes a size for the debris of 4 ft. long and 4 in. diameter.

CWD ( ft3 / ac ) Variable Index

greater than 86 1.0

70 - 85 0.7

55 - 69 0.5

40 - 54 0.2

less than 40 0.1

site converted 0.0

 Soil Quality (Vsoilq)

This variable represents the physical integrity of the soil above the Bg or Btg horizon. This includes the number and continuity of pores and the type, grade, and size of soil structure. Measurement of soil condition will involve looking at roots, pores (abundance, size, and continuity), and soil friability (rupture resistance, from very friable to very friable and harder. Measurement is done on the more limiting part of the A horizon, directly above the Bg or Btg horizon. The Soil Quality Index (SQI) will be assigned for each of the three measured soil parameters. The points for each soil parameter will then be added. The Vsoilq index will be assigned based upon the total for the three soil parameters.

Pores: The quality and continuity of soil pores received a quantitative score of 1 through 3. Many fine and very fine pores in the A horizon receive a score of 3. Common pores receive a score of 2, and few pores a score of 1. Any deviation from the standard may be an indication that the site is not functioning to full capacity hydrologically. Less evidence of macropores indicates less water moving downward through the soil profile to recharge the water table. Nonmatrix and interstructural porosity have particular importance for water movement.

Consistence (Moisture): Consistence is now called "Rupture Resistance Classes for Block-like Specimens, slightly dry and wetter." Very friable and friable rupture resistance in the A horizon was indicated by a score of 3. Firm was indicated by a score of 2, and very firm or harder by a score of 1. This measure is an indication of compaction, which increases bulk density, which in turn reduces porosity.

Structure: Soil structure was rated according to the following metrics. Structure that was "Weak or moderate subangular blocky parting to moderate fine and medium subangular blocky parting to fine and medium granular" in the A horizon was noted by a score of 3. Fine to medium subangular blocky parting to granulate in the A horizon was scored as a 2. Massive or coarse subangular blocky or evidence of a plowpan were designated as a 1. A plowpan was indicated in the field by dense coarse, or massive, structure, and roots growing horizontally across the top of the pan.

Soil Quality Index Score Variable Index

greater than or equal to 7 1.0

4 - 6 0.5

less than or equal to 3 0.1

substrate is concrete, or non-porous 0.0

Material for this variable was provided by Leander Brown, NRCS Wetland Science Institute.

 Index of Function

FCIcycle = ( Vsoilq+ Vba + ( Vsnag4 + Vcwd )/2 + FCIhydro ) / 4

 Maintenance of Characteristic Habitat

Definition: This function focuses on the structure and composition of the habitat within the assessment area.

Discussion and Rational of Function: This function was recognized as a composite of specific sub-functions during the work session. The specific sub-functions are maintain characteristic plant community, maintain vertical habitat structure, and maintain typical abundance of animals.

Wet Flats in relatively undistrubed settings exhibit a large range of wildlife benefits. Many animals, ranging from large game to small amphibians, count on wet flats for a great portion of their subsistence. Much of the wildlife depends on the deciduous flats ability to produce and sustain a viable population of hardmast producers, as well as large standing dead trees for wildlife cavities and an appropriate amount of ground cover such as coarse woody debris. Likewise, many small animals benefit from the microtopography that occurs when trees fall over and leave ponded water for long periods of time.

Variable Descriptions:

Biomass of Hardwood Canopy (Vba)

This variable is a surrogate for the amount of nutrients and compounds held in the tree layer, the amount of nutrients and compounds the tree layer takes up, and the nutrient cycling which occurs at any oxidized rhizospheres around the tree roots. For the purposes of this variable, only hardwood canopy trees should be considered. The trees considered are only those greater than 6 in (15 cm) dbh. This variable provides an indication of the forest maturity and living forest biomass.

Hardwood Basal Area Variable Index

greater than 125 ft2/ac 1.0

100 - 125 0.7

75 - 99 0.3

less than 75 0.1

Not restorable 0.0

 Regeneration of Canopy Species (Vregen )

This variable is the density of saplings of the dominant canopy trees. This provides some measure of whether the site is self-maintaining. If the site has been drained or similarily impacted, the species in the sapling layer should be different (less hydrophytic) than the canopy layer. This variable should be the tree species between 10 -20 ft. tall and less than 4 in. in diameter. To be included in the count, the sapling species need to occur on the list in Appendix B of tree species that characteristically occur.

Regeneration Variable Index

Vigorous stand of saplings and

>80 % of species occur on list 1.0

Saplings present and > 60% occur

on list 0.5

Few saplings and/or < 60% occur

on list 0.3

No sapling regeneration or

fewer than 40% occur on list 0.1

Site converted and no restoration possible 0.0

 Hard Mast Production (Vmastpro)

This variable is a measure of the hard mast production available for wildlife consumption. The species of hard mast producers are listed in Appendix B. This variable is closely related to Vba. To determine the value for Vmastpro, it is necessary to determine the percentage of the basal area which is due to hard mast producing species.

% of Vba due to Hard Mast Species Variable Index

greater than 25% 1.0

15 - 25% 0.7

10 - 14% 0.5

less than 10% 0.1

site converted 0.0

Biomass of Standing Dead Trees (Vsnag8)

This variable represents the biomass of standing dead trees greater than 8 inches in diameter and greater than 15 ft tall. Standing dead trees is one component of detrital biomass available for nutrient cycling. This variable is measured by using the point-center-quarter method (Brookhout 1996). A point is established in the center of the wetland assessment area / sampling area and quarters are established by setting up perpendicular lines crossing at the center point. The distance to the closest snag (meeting the above size criteria) is measured, if within 225 ft., in each quarter. If the distance is greater than 225 ft., or no snag is visible in that quarter, use 225 ft. So, four measures should be made, one for each quarter of the circle and an average distance is calculated. The average distance is used in the following formula to determine the density of 8 in diameter snags.

Density of 8 in. Snags = 43560 / (avg. distance)2

8 in. Snags/Acre Variable Index

greater than 5 1.0

4 - 5 0.7

2 - 3 0.3

1 0.1

site converted 0.0

 Biomass of Coarse Woody Debris (Vcwd)

This variable represents the accumulation of dead woody material which is available for nutrient cycling. For the purposes of this variable, the debris must be 4 inches or greater in diameter, and over 3 feet long to count. This variable is to be measured using a modified version of the point-center-quarter method. A point is established in the center of the wetland assessment area / sampling area and quarters are established by setting up perpendicular lines crossing at the center point. The distance to the closest coarse woody debris (meeting the above size criteria) is measured, if within 225 ft., in each quarter. If the distance is greater than 225 ft., or no coarse woody debris is visible in that quarter, use 225 ft. So, four measures should be made, one for each quarter of the circle and an average distance is calculated. The average distance is used in the following formula to determine the density of coarse woody debris.

CWD = 15175 / (average distance)2

The numerator (15175) in the above equation is a factor to convert the density version of the point-center-quarter method into a volumetric term. Using this factor assumes a size for the debris of 4 ft. long and 4 in. diameter.

CWD ( ft3 / ac ) Variable Index

greater than 86 1.0

70 - 85 0.7

55 - 69 0.5

40 - 54 0.2

less than 40 0.1

site converted 0.0

Index of Function

FCIhabitat = (Vba + Vregen + Vmastpro + Vsnag8 + Vcwd) / 5

 Landscape Support

Definition: This function can also be titled as Maintain Habitat Interspersion and Connectivity. It is a measurement of the type and quality of the surrounding land use, and the size of those areas.

Discussion and Rational of Function: Wetlands of any kind and size are influenced by the surrounding landscape in several functions. However, landscape support (or surrounding landuse) is critical in determining the quality and accessibility of a wetland for wildlife. If a wetland assessment area (WAA) is surrounded by natural areas the accessibility is certainly greater than any area that is surrounded or bordered by anthropogenic activities. The size of the natural area to which the WAA is connected also is an important factor. Size has a direct impact on the type and number of species that use an area.

Variable Descriptions:

Contiguous Forested Habitat (Varea)

This variable is a measure of habitat fragmentation. Historically, deciduous wet flats were thought to be large tracts and connected to other forms of wooded habitat. These large expanses were able to support numerous species of wildlife, including species requiring large ranges such as black bears. This variable can be determined by using aerial photography and ground truthing the size of contiguous tracts. In order to include an area as contiguous, there must be a minimum width of 75 ft.

Contiguous Wooded Area Variable Index

greater than 500 acres 1.0

250 - 500 0.7

100 - 249 0.3

less than 100 0.1

Landuse Patterns (Vlandpat)

This variable takes into account landuse patterns for the area around the wetland assessment area. Tables showing various landuses have been included in Appendix C. The landuses have been categorized to show relative impacts to habitat. Four categories have been assigned. Category 1 has been set up to show relatively undisturbed landscapes, such as forested areas. Category 4 has been set up to show highly disturbed landscapes, such as roads, parking lots and commercial development. Categories 2 & 3 fall in between. The percentages of each landuse category are determined within a 1 mile radius around the site, and a weighted average calculated.

Landuse Category Variable Index

Category 1 1.0

Category 2 0.5

Category 3 0.1

Category 4 0.0

Weighted Landuse = [(% Cat. 1 X 1.0) + (% Cat. 2 X 0.5) + (% Cat. 3 X 0.3) + (% Cat. 4 X 0)] / 100

It is intended that the information necessary to determine the Weighted Landuse Categories be gathered in the office prior to evaluating the site in the field. Recent aerial photography can be used to determine the landuse of the surrounding area.

Index of Function

FCIlandscape = (Vlandpat + Varea) / 2

 Variable Usage in Functions

Functions

F1: Maintenance of Characteristic Hydrologic Regime

F2: Maintenance of Characteristic Biogeochemical Transformations

F3: Maintenance of Characteristic Habitat

F4: Landscape Support

Variables

F1

F2

F3

F4

Varea      

X

Vba  

X

X

 
Vcwd  

X

X

 
Vdam

X

     
Vdrain

X

     
Vet

X

     
Vlandpat      

X

Vmastpro    

X

 
Vregen    

X

 
Vsnag4  

X

   
Vsnag8    

X

 
Vsoilq

X

X

   
Vvol

X

     

Appendix A

Hydrology Sketches and Lists

Figure 1 -- Zonation for Vdrain

d1: distance from ditch with wetland hydrology removed

 

d2: distance from ditch with impacted hydrology

 

d2 - d1: value used to calculate area of Zone1

 

Zone 1: portion of WAA with wetland hydrology removed

 

Zone 2: portion of WAA with impacted wetland hydrology

 

Zone 3: unimpacted portion of the WAA

 

 Table 1 -- North Carolina and Virginia soil series expected to occur on wet flats and the textural class.

Soil Series

State

Group

Acredale

VA

2

Arapahoe

NC

3

Backbay

VA

2

Ballahak

NC

2

Bayboro

NC

1

Cape Fear

NC

1

Chickahominy

VA

1

Conaby

NC

3

Coxville

NC

1

Deloss

NC

2

Elkton

VA

2

Fallingston

VA

2

Featherstone

VA

2

Fortescue

NC

2

Grantham

NC

2

Grifton

NC

2

Hobucken

NC

3

Hyde

NC

2

Johnston

NC

3

Lenoir

NC

1

Liddell

NC

2

Masontown

NC

3

Murville

NC

3

Nakina

NC

2

Nimmo

VA

3

Othello

VA

2

Pantego

NC

2

Pasquotank

NC

2

Perquimans

NC

2

Pettigrew

NC

1

Pocomoke

VA

3

Polawana

VA

3

Roanoke

VA

1

Roper

NC

2

Toisnot

NC

3

Tomotley

NC

2

Torhunta

NC

3

Wasda

NC

2

Weeksville

NC

2

Wilbanks

NC

1

Woodington

NC

3

If a needed soil series does not appear on the list, contact a Soil Scientist to determine which series is closest to the actual needed series. This list is intended to be complete, but it is possible that the list contains soils which usually do not occur on wet flats or that some soils have been omitted. Please contact the NRCS SE Coastal States Wetlands Team with suggested changes.

 Table 2 -- Distances for Zones

Category 1 Soils

Ditch Depth (feet)

Distance 1 (feet)

Distance 2 (feet)

1

50

80

2

95

150

3

120

195

4

140

225

Category 2 Soils

Ditch Depth (feet)

Distance 1 (feet)

Distance 2 (feet)

1

70

120

2

135

220

3

175

280

4

205

325

 Category 3 Soils

Ditch Depth (feet)

Distance 1 (feet)

Distance (feet)

1

95

155

2

180

285

3

230

365

4

265

420

Note: This material is based upon a method of evaluating drainage by the SE Coastal States Wetlands Team for use in the HGM Mineral Flats model being developed by R. Rheinhardt. Version 1 of the interim model relies on calculations done for South Carolina soil series (including some series from both Georgia and North Carolina). The material in Table 1 is specifically for NC & VA and will be incorporated into the calculations for later versions of the model.

 Figure 2 -- Areas for Vdam

 

 

Area 1: portion of WAA not impacted by the flow impediment

 

Area 2: portion of WAA upstream of the flow impediment

 

Area 3: area of the flow impediment

 

Area 4: portion of WAA downstream of the flow impediment -- assumed to be equal in size to Area 2

 

 

 

Appendix B

Vegetation Lists

 Hardwood Canopy Species for Vba and Vregen

Acer rubrum Red Maple

Fraxinus spp. Ash spp.

Liquidambar styraciflua Sweetgum

Quercus falcata Southern Red Oak

Quercus michauxii Swamp Chestnut

Lirodenron tulipifera Tulip-Tree

Quercus phellos Willow Oak

Taxodium distichum Bald Cypress

Quercus laurifolia Laurel Oak

Nyssa sylvatica var. biflora Black Gum

Quercus pagodifolia Cherrybark Oak

Ulmus americana American Elm

Ulmus rubra Slippery Elm

Hard Mast Producing Species for Vmastpro

Quercus falcata Southern Red Oak

Quercus michauxii Swamp Chestnut

Quercus phellos Willow Oak

Quercus laurifolia Laurel Oak

Quercus pagodifolia Cherrybark Oak

Appendix C

Landuse Categories

Category 1: Woods

Woods - grass combination (orchard or tree farm)

Protected natural areas

Category 2: Meadow / Hayland - continuous grass, protected

High intensity tree farm

Category 3: Row Crops

Residential, ³ 1/2 acre lots

Gravel or dirt roads

Pasture with grazing

Recent clear cut area

Category 4: Paved streets and roads

Parking Lots

Commercial and Businesses

Industrial

Residential, < 1/2 acre lots

Newly graded areas

 Literature Cited

Bookhout, T.A., ed. Research and Management Techniques for Wildlife and Habitats. Bethesda, MD: The Wildlife Society, 1996. pp 575-577.

Fretwell, J.D., J.S. Williams, and P.J. Redman (compilers). 1996. National Water Summary On Wetland Resources. United States Geological Survey, Water Supply Paper 2425. pp. 7-14.

Mitsch, W.J., and J.G. Gosselink. 1993. Wetlands (second edition) New York, NY, Von Nostrand Reinhold. pp 100-102.

United States Department of Agriculture, Natural Resources Conservation Service. 1996. Field Indicators of Hydric Soils in the United States. G.W. Hurt, P.M. Whited, and Pringle, R.F. (eds,). USDA, NRCS, Fort Worth, TX.

United States Department of Agriculture, Natural Resources Conservation Service. 1997. National Engineering Field Handbook, Ch19, "Hydrology Tools for Wetland Determination."

USDA, NRCS. pp 37 - 40.

United States Department of Agriculture, Soil Conservation Service. 1981. Agriculture Handbook 296, "Land Resource Regions and Major Land Resource Areas of the United States." USDA, SCS. Washington, DC.

Southeast Forested Depressional Wetlands Hydrogeomorphic Method

  Modified and compiled by N. Eric Fleming, and J. Glenn Sandifer, Jr.,

Southeast Coastal States Wetlands Team, USDA, Natural Resources Conservation Service

Field Workgroup: Tom Counts, NRCS AL; Art Hosey, USACE, Mobile District; John Vance, NRCS FL; Rosalind Moore, NRCS FL; Jeff Allen, NRCS FL; Stuart Santos, USACE, Jacksonville District; Louis Justice, NRCS GA; Tom Fischer, USACE Savannah District; Robert Brooks, USFWS GA; James W. Lewis, Jr., NRCS SC; and Jake Duncan, USACE, Charleston District

 Preface

This document was prepared for use in southern Alabama, Georgia, the pan-handle of Florida, and the coastal plain of South Carolina. The NRCS Land Resource Regions (LRR’s) which encompass the area are P and T. Specifically, the Major Land Resource Areas (MLRA’s) are 133A, 152A, 153A, and 153B. LRR P is titled the South Atlantic and Gulf Slope Cash Crops, Forest, and Livestock Region and consists of the gently sloping to rolling southern Piedmont and upper Coastal Plain. LRR T is titled the Atlantic and Gulf Coast Lowland Forest and Crop Region and consists of the nearly level low parts of the Atlantic and Gulf Coastal Plains (USDA, 1981).

The original format and many of the variables of the interim method rely upon the Peninsular Florida Herbaceous Depressional Wetlands Hydrogeomorphic Regional Guidebook (Trott, et al. 1997) as a guide. However, as the interim method filled out, the similarity diminished due to information from other sources and comments from workgroup participants and reviewers.

The Florida Depressional model was presented to a work-group composed of NRCS, USACOE, and USFWS personnel from Alabama, Florida, Georgia, and South Carolina at a session in Albany, GA the week of August 25, 1997. The group commented on the use of the model structure, its variables, and the variable scaling at several forested depressional wetland sites. The NRCS Southeast Coastal States Wetlands Team agreed to modify the existing model and incorporate the comments of the interagency group to create a draft forested depressional HGM method. The intent of this effort is to create interim HGM models for NRCS’s use under the 1996 Farm Bill (the Federal Agriculture Improvement and Reform Act of 1996, FAIRA) which can later be tied to reference sites and developed into full HGM models. This process was used to meet NRCS’s requirements of having procedures in place to meet the new wetland flexibility provisions of the Farm Bill while still generating a product which can be refined in the future for more rigorous applications. The prevailing opinion of the Albany workgroup was that basing the effort on an existing model which has been through at least some level of review and comment will give the resulting interim method a more solid basis from which to start.

The draft forested depression method is to be forwarded to the workgroup participants for comments. After comments are incorporated, the intent is to field test the resulting interim models in each of the above mentioned states. The process of field testing will allow data collection to begin as well as the selection of reference sites for variable scaling.

This document encompasses a large area geographically and most likely numerous subclasses. The intent is to provide a broad first approximation for the interim HGM process. Specific models for given subclasses will need to be scaled individually. By using a general functional assessment approach based upon the same method for all depressional wetlands in the southeast, consistency across state lines can be achieved.

Note: Variables which are being eliminated have been included in this initial version to highlight potential changes in format from the FL Herbaceous Depressions model. Subsequent versions will not have this material included.

 Wetlands of the Southeast

Wetlands in Alabama

Wetlands cover about 10 percent of Alabama and range in size from small areas of less than an acre to the 100,000 acre forested tract in the Mobile-Tensaw River Delta. Most of the State’s forested wetlands are bottom-land forests in alluvial flood plains. Coastal waters support extensive salt marshes. Wetland acreage in the area that is now Alabama has been agricultural and silvicultural conversions in the interior; dredging on the coast; industrial, commercial, and residential development; erosion; subsidence; and natural succession of vegetation. (Fretwell et al. 1996)

Wetlands in Florida

Florida has about 11 million acres of wetlands, more than any of the other 47 conterminous States. The abundance of wetlands in Florida is due primarily to the low, flat terrain and plentiful rainfall. Most of Florida’s wetlands are forested freshwater habitats on stream flood plains, in small depressions and ponds, and covering wet flatwoods. The Everglades, in southern Florida, is a large freshwater marsh that once received surface-and ground-water flows from the Kissimmee River-Lake Okeechobee Basin but which now depends on water releases from canals and water-retention areas. Florida has lost nearly one-half of its wetlands, primarily to agricultural drainage. The State protects wetlands by regulating development in wetland areas, acquiring wetlands and land adjacent to wetlands, and requiring local governments to produce long-range plans for wetland protection. (Fretwell et al. 1996)

Wetlands in Georgia

Georgia has more than 7.7 million acres of wetlands. Georgia’s wetlands are diverse, ranging form mountain seepage areas to estuarine tidal flats. This diversity is primarily due to the wide variety of landforms present, each of which can have different geologic and hydrologic characteristics. The greatest acreages of wetlands are in the coastal plain, where flood-plain wetlands are most extensive and tidal freshwater swamps and estuarine marshes meet. Most of Georgia’s wetlands are forested freshwater habitats associated with streams. The Okefenokee Swamp in Georgia, one of the largest freshwater wetlands in the United States, is a mosaic of emergent marshes, aquatic beds, forested and scrub-shrub wetlands, and forested uplands. (Fretwell et al. 1996)

Wetlands in South Carolina

Nearly one-quarter of South Carolina is wetland - about 4.6 million acres. South Carolina’s wetlands provide flood attenuation, erosion control, water quality maintenance, recreational opportunities, and fish and wildlife habitat. South Carolina wetlands are important wintering areas for migratory waterfowl on the Atlantic Flyway. Wetlands in the State include wet pine flatwoods, pocosins, Carolina bays, beaver ponds, bottom-land forests, swamps, fresh and salt marshes, and tidal flats. About 80 percent of the wetlands are freshwater and forested. Wetland acreage in South Carolina has declined by more than one-quarter since the late 1700’s, primarily as a result of human activities. (Fretwell et al. 1996)

 Forested Depressions

Forested, freshwater wetlands have been classified in a variety of ways. These wetlands are primarily palustrine forested (Cowardin 1979). The United States Department of Interior, Fish and Wildlife Service’s National Wetlands Inventory maps show the sites as follow: PFO1, PFO2, PFO3. These wetlands also are know by a variety of common names. Some of these names are as follow: Grady ponds, Carolina bays, cypress domes, cypress ponds, bays, gum ponds, etc. The HGM classification is depressional. The main characteristic of these wetlands is a closed topographic contour (a topographic depression). The hydrology source is overland flow from the surrounding drainage area, direct precipitation, and in some cases groundwater fluctuations. Depending upon the location and landscape setting, there can be a variety of hydrologic regimes ranging from intermittently flooded to semipermanently flooded and even permanently flooded in the lowest portions of the depression. Some of the conversion activities usually associated with this wetland type include clearing, drainage, filling, excavation and inundation. The vegetation in these wetlands can range from facultative upland (FACU) to obligate (OBL) indicator status, depending on the hydrologic regime and position in the wetland. Typical species are listed by state and regions for use in the vegetation function of the model in Appendix C.

Depressions in southern Alabama .....description of the variance in landforms, hydroperiods, geology etc.

Potential subclasses for Alabama

Depressions in northern Florida.... description of the variance in landforms, hydroperiods, geology etc.

Potential subclasses for Florida

Depressions in Georgia are found primarily in the southwestern portion of the state in a landscape of limesinks and ancient marine deposits. The sources of the wetland hydrology can be precipitation and runoff, precipitation and groundwater, and also runoff and groundwater. The most common impact associated with agriculture is removing the trees and filling a portion of the depression for center-pivot irrigation system travel ways. Differences in the duration of ponding and saturation will be the most probable basis for subclasses.

Depressions in South Carolina are found primarily in a landscape of agriculture and forestry. The hydroperiods range from seasonally saturated to semi-permanently flooded. Typical impacts are largely due to agriculture and forestry such as farming, drainage, partial drainage, filling and excavation for ponds. Potential subclasses for South Carolina could be based on dominant vegetation (broadleaf deciduous, needle leaf deciduous, and needle leaf evergreen) and hydroperiods (saturated, seasonally flooded, and semi-permanently flooded.

 Functional Profile

Maintenance of Characteristic Hydrologic Regime

Definition: The ability of a wetland to maintain its normal hydroperiod by storing water from overland flow, direct precipitation, and/or saturated and unsaturated subsurface discharge. The function can be quantified as an index of depth, duration, and frequency of inundation.

Discussion and Rational: Depressional wetlands in the defined domain of this model exhibit a wide range of hydroperiods due to various factors such as the water source, the geology, the watershed size, the soils, evapotranspiration rates, and the presence or absence of outlets. The basic alterations to the wetland hydrology are increasing the amount of water, decreasing the amount of water, and/or changing the storage characteristics of the depression. Increasing the amount of water includes alterations which change the runoff contributing watershed by paving portions of it, removing natural vegetation, or even changing the size of the watershed such as diverting additional drainage area into the depression. Decreasing the amount of water would include diverting drainage area from the depression and drainage activities such as construction of an outlet ditch. Changing the storage characteristics involves actual changes in the depression size due to fill or excavation. All of these changes cause both the wetland’s hydroperiod and hydrodynamics to differ from reference standard condition.

Variable Descriptions:

Watershed Size (Vwshed)

This variable represents changes in size of the historic watershed of the depression in comparison to the current watershed of the depression. If the historic watershed was larger, and a portion of it has been altered so that it no longer contributes runoff to the depression (such as a road fill blocks overland flow to the depression, or ditching forces the water to flow in a different direction) a ratio is calculated by dividing the current watershed size by the historic watershed size and the result is entered into the following table. If the historical watershed was smaller, and additional drainage area is added to the depression (such as a ditch system using the depression as an outlet) a ratio is calculated by dividing the historical watershed size by the current watershed size and the result is entered into the following table. Both of these cases rely on the concept that changes in reference condition result in non-standard conditions and a score less than one.

Size Ratio Variable Score

0.90 - 1.00 1.0

0.75 - 0.89 0.7

0.50 - 0.74 0.5

0.25 - 0.49 0.3

0.00 - 0.24 0.0

 Surrounding Landuse (Vluse)

[formerly Surface Water Runoff Vrunoff]

This variable represents overland flow from the contributing watershed which enters the depression. Primarily, the variable deals with changes in the watershed which will affect the quantity and timing of runoff to the depression. The most common effects are reduced infiltration and decreased travel time, which significantly increase peak discharges and runoff. Runoff is determined primarily by the amount of precipitation and by infiltration characteristics related to soil type, soil moisture, antecedent rainfall, cover type, impervious surfaces, and surface retention. Travel time is determined primarily by slope, length of flow path, depth of flow, and roughness of flow surfaces (USDA 1986). For the purposes of this model, a modified version of NRCS’s Curve Number Hydrology is used. A curve number is assigned for each landuse and hydrologic soil group and a weighted curve number is calculated using the curve numbers found in Appendix A (tables from TR-55). The resulting weighted curve number is entered into the following table and the variable index is found.

Weighted Curve Number Variable Index

less than 70 1.0

71 - 80 0.7

80 - 85 0.5

85 - 90 0.1

greater than 90 0.0

The variable index is based upon the logic that the historic watershed contributing runoff to the depression was forested, in fair to good hydrologic condition, and non-hydric soils (not hydrologic soil group D). These conditions would result in a weighted curve number ranging approximately 60 - 65 (see Appendix A for Curve Numbers from TR-55) and a variable index of one. The next category (71-80) should generally represent agricultural crops with conservation tillage, pastures, and woods in poor condition (heavy grazing, etc.). The third category (80-85) should generally represent agricultural crops without conservation tillage, residential areas with larger lots (greater than 1/4 acres), fully develop urban areas (vegetation established) such as golf courses, parks, etc. The fourth category (85-90) should represent dirt roads, some commercial areas, small residential lots, and newly graded areas. The last category (>90) should represent large amounts of impervious area such as roads, and parking lots.

It is intended that the information necessary to determine the variable index be figured in the office prior to evaluating the site in the field. Recent aerial photography can be used to determine the landuse of the contributing watershed. If information showing which hydrologic soils group a particular soil series falls within is unavailable, an assumption that equal percentages of group B & C soils occur in each of the landuse areas. The variable index will be used repeatedly in the other functions of this model.

In cases where there is no contributing watershed, Vluse is set equal to 1 except in Maintenance of Distribution and Abundance of Wildlife (F4). In this case a value for Vluse is calculated using a 1000 ft radius around the depression.

 Wetland Water Storage Capacity (Vprofile)

This variable represents changes in the storage volume of the depression due to excavation and/or filling activities in the depressional area. The changes in storage volume can be estimated visually for routine assessment and the percentage disturbed is then entered into the following table. For a more comprehensive approach, the actual change in volume can be calculated and the calculated percentage change in volume can then be entered into the table. It is important to recognize that this variable is dependent upon volume, not surface area. Filling a large area with a small thickness of material can be the same volume as a small area filled with a large thickness of material. For the purposes of this variable the analogy of a bowl filled with water can be used. This variable only focuses upon the amount of water in the bowl, not any other impacts associated with filling or excavating.

% Wetland Volume Disturbed Variable Index

0 - 9 1.0

10 - 29 0.8

30 - 49 0.6

50 - 69 0.3

70 - 100 0.1

unrestorable (paved) 0.0

 Tree Cover (Vtree)

[formerly Evapotranspiration Vet]

This variable represents the evaporation potential of the free water surfaces in the depressional area and the transpiration of the vegetation. To some extent, these factors are offsetting. For densely vegetated sites, most of the evapotranspiration (ET) is in the form of transpiration because of limited free water surface for evaporation. For nonvegetated sites, the ET will be entirely evaporation and no transpiration will occur. However, as this phenomenon relies upon an open water surface from which water can evaporate, and many (if not most) of the depressions do not have a hydroperiod which results in a free water surface for an extended period of time (and if water is present on the surface it should be covered by vegetation in a reference standard site), the presence of vegetation should "pump" water out of the soil profile as transpiration. The general unimportance of vegetation-species variation on overall wetland water loss is probably a reasonable conclusion for most wetlands, although it is clear that the type of wetland ecosystem and the season are important considerations (Mitsch and Gosselink 1993). Because of this, it follows that it is the presence and amount of vegetation which is critical, rather than the specific type of vegetation. Intuitively, in a forested system, trees will be able to remove water from deeper in the soil profile because of a more extensive root system. If the trees are removed, the system will stay saturated longer and the saturation will be higher in the profile.

For interim model purposes, Vtree should be estimated by the percent canopy cover of the tree layer.

% Canopy Cover of Trees Variable Index

80 - 100 1.0

60 - 79 0.7

40 - 59 0.3

less than 40 0.1

Not restorable 0.0

Constructed Wetland Outlet (Voutlet)

This variable represents the effects of drainage on the depressional wetland, which alters both the hydroperiod and the hydrodynamics of the wetland. For routine assessments, this variable is a visual estimate of the alterations made to the depressional wetland, which is scaled in the following table. The comprehensive method is to calculate the extent of the drainage using hydrology tools (such as Kirkham’s equation for surface ponding and the van Schilfgaarde, Ellipse, or Hooghoudt equation for drainage ditches) (USDA 1997). For the purposes of this method, static storage may be thought of as relatively long-term water levels and dynamic storage may be thought of as the short-term rise and fall in the depression from a rainfall event.

Drainage Impact Variable Index

No outlet or no modification to

natural outlet. 1.0

Outlet elevation lowered to reduce detention

time of dynamic storage but some

static storage remains. 0.5

Outlet invert lowered to significantly reduce

dynamic and static storage. 0.3

Outlet invert lowered to drain wetland 0.1

(ditch elevation at or below bottom of depression)

Wetland is drained and no restoration possible 0.0

 Constructed Wetland Inlet (Vinlet)

This variable represents changes to the hydrology of the depressional wetland due to structures adding water to the wetland from sources not naturally connected to the wetland. An example of this could be a drainage ditch which drains adjacent uplands and/or other nearby depressions which outlets into the depressional wetland. The routine assessment is a visual inventory of the structure(s) and the extent of the alteration which is scaled in the following table. The comprehensive method is to calculate the extend of the modification by use of standard hydraulics, i.e. Manning’s equation for a ditch.

Inlet Modification Variable Index

No inlet (point source) is present

or no modification to natural inlet. 1.0

Sufficient water is added to increase

static storage or enough natural flow is blocked

to reduce dynamic storage. 0.5

Sufficient water is added to significantly

increase static storage or enough natural

flow is blocked to reduce static storage. 0.1

Wetland is permanently flooded by a structure

or is cut off from water sources entirely. 0.0

Regional Groundwater Level (Vregion)

This variable represents drawdowns of the regional water table due to large wells, especially around municipal well fields and exceptionally large agricultural irrigation wells. This variable is intended to be used only in situations where there is information indicating a regional drawdown is occurring. The field workgroup indicated mixed feelings whether this variable should be included or not since it was originally included in the Florida Herbaceous Depressional Wetlands HGM model to address situations in south Florida. The consensus was that the variable should be included in order to address rare situations, and that in the vast majority of cases, by default, the variable will be equal to one.

Measure Variable Index

Wetland is not near a municipal well

or large agricultural well. 1.0

Wetland is between 2,500 - 10,000 feet from

municipal well field or 1,000 - 5,000 feet

from large agricultural well

(with known drawdown). 0.5

Wetland is within 2,500 feet of municipal well

or within 1,000 feet of large agricultural well. 0.1

Wetland hydrology removed due to drawdown 0.0

 Wetland Hydrology (Vwet)

This variable is defined as whether or not the wetland exhibits a hydrologic regime which is characteristic of its subclass. Evidence of the characteristic regime is necessary to verify wetland hydrology throughout the wetland. This variable was primarily included in the Florida Herbaceous Depressional Wetlands HGM model to eliminate situations where the site could exhibit reference standard conditions for all the other variables in the hydrology function, yet still not meet regulatory wetland hydrology (no alterations to the depression and the surrounding land, but no wetland hydrology). This variable is being eliminated from the interim model because impacts which remove wetland hydrology should be shown by one of the existing variables.

 Soil Quality (Vsoilq)

This variable represents the physical integrity of the soil above the Bg or Btg horizon. This includes the number and continuity of pores and the type, grade, and size of soil structure. Measurement of soil condition will involve looking at roots, pores (abundance, size, and continuity), and soil friability (rupture resistance, from very friable to very friable and harder. Measurement is done on the more limiting part of the A horizon, directly above the Bg or Btg horizon. The Soil Quality Index (SQI) will be assigned for each of the three measured soil parameters. The points for each soil parameter will then be added. The Vsoilq index will be assigned based upon the total for the three soil parameters.

Pores: The quality and continuity of soil pores received a quantitative score of 1 through 3. Many fine and very fine pores in the A horizon receive a score of 3. Common pores receive a score of 2, and few pores a score of 1. Any deviation from the standard may be an indication that the site is not functioning to full capacity hydrologically. Less evidence of macropores indicates less water moving downward through the soil profile to recharge the water table. Nonmatrix and interstructural porosity have particular importance for water movement.

Consistence (Moisture): Consistence is now called "Rupture Resistance Classes for Block-like Specimens, slightly dry and wetter." Very friable and friable rupture resistance in the A horizon was indicated by a score of 3. Firm was indicated by a score of 2, and very firm or harder by a score of 1. This measure is an indication of compaction, which increases bulk density, which in turn reduces porosity.

Structure: Soil structure was rated according to the following metrics. Structure that was "Weak or moderate subangular blocky parting to moderate fine and medium subangular blocky parting to fine and medium granular" in the A horizon was noted by a score of 3. Fine to medium subangular blocky parting to granulate in the A horizon was scored as a 2. Massive or coarse subangular blocky or evidence of a plowpan were designated as a 1. A plowpan was indicated in the field by dense coarse, or massive, structure, and roots growing horizontally across the top of the pan.

Soil Quality Index Score Variable Index

greater than or equal to 7 1.0

4 - 6 0.5

less than or equal to 3 0.1

substrate is concrete, or non-porous 0.0

 Index of Function

FCIhydro = minimum of [ (Vluse + Vwshed ) / 2 or (Vprofile + Vtree + Vsoilq) / 2 or Voutlet or Vinlet or Vregion ]

 Cycling of Nutrients and Compounds

Definition: Biological, chemical and physical processes which cycle compounds from one form into another. This function can be quantified in tons/acre/year of nutrients and compounds as the basic mass balance of the wetland.

Discussion and Rational: Phosphorus, nitrogen, carbon, and other elements are found in various forms in the water, soil, plants, microbes, animals, detritus, etc. These elements are in a constant state of flux as they cycle from one form to another. The model assumes that if the producers and decomposers are intact that biotic cycling of nutrients and compounds will proceed at reference standard rates. Therefore, variables are used which estimate the amount and type of plant material that is present to assimilate the nutrients and compounds, as well as variables to estimate the amount of decaying material available to release nutrients and compounds (Trott et al.). The abiotic portion of the cycling is primarily dependent upon the adsorption of materials to soils, solubilities of materials in water that are available for export, the amount of water that leaves the wetland carrying dissolved materials, the hydroperiod to maintain anaerobic conditions, and the importation of from surrounding areas (Trott et al.).

Variable Descriptions:

Tree Cover (Vtree)

This variable is a surrogate for the amount of nutrients and compounds held in the tree layer, the amount of nutrients and compounds the tree layer takes up, and the nutrient cycling which occurs at any oxidized rhizospheres around the tree roots. For interim model purposes, Vtree should be estimated by the percent canopy cover of the tree layer and entered into the following table. This method allows the use of information previously determined from the wetland delineation.

% Canopy Cover of Trees Variable Index

80 - 100 1.0

60 - 79 0.7

40 - 59 0.3

less than 40 0.1

Not restorable 0.0

Shrub Density (Vshrub)

This variable is a surrogate for the amount of nutrients and compounds held in the shrub layer, the amount of nutrients and compounds the shrub layer takes up, and the nutrient cycling which occurs at any oxidized rhizospheres around shrub roots. For the routine assessment procedure, the percentage cover of the shrub layer is used. The comprehensive assessment is an actual count of the number of stems of woody vegetation greater than 3 feet tall, not falling into the tree class in a 0.01 acre plot (approximately 21 ft. X 21 ft. or approximately a 12 ft. radius circle) (Trott et al). The resulting value (for both procedures) is entered into the following table to find the corresponding variable value.

% Shrub Cover Variable Index

40 - 60 1.0

20 - 39 or 61 - 80 0.5

1 - 19 or 81 - 99 0.2

0 or 100 0.1

 Groundcover (Vgrndcvr)

This variable is a surrogate for the amount of nutrients and compounds held in the herbaceous layer, the amount of nutrients and compounds the herbaceous layer takes up, and the nutrient cycling which occurs at any oxidized rhizospheres around the roots. For the routine assessment procedure, the percent cover of the herbaceous layer is estimated. The comprehensive assessment is the percentage cover in a 1.1 yard2 plot (1meter2, or approximately 3.1 ft. X 3.1 ft.) (Trott et al). The resulting value (for both procedures) is entered into the following table to find the corresponding variable value.

% Herbaceous Groundcover Variable Index

20 - 40 1.0

1 - 19 or 41 - 60 0.5

0 or 61 - 80 0.2

81 - 100 0.1

Constructed Outlet (Voutlet)

This variable represents the effects of drainage on the depressional wetland, which alters both the hydroperiod and the hydrodynamics of the wetland. For routine assessments, this variable is a visual estimate of the alterations made to the depressional wetland, which is scaled in table T4. The comprehensive method is to calculate the extent of the drainage using hydrology tools (such as Kirkham’s equation for surface ponding and the van Schilfgaarde, Ellipse, or Hooghoudt equation for drainage ditches) (Woodward et al. 1996???). For the Nutrient Cycling function this variable shows the change in the amount of nutrients and compounds the wetland has available to cycle. If an artificial outlet is present, it lowers the quantity of nutrients and compounds as well as decreasing the residence time in the wetland for cycling to occur. However, since Voutlet is already included in the hydrology function as a variable, and if an outlet significantly reduces the hydroperiod. Voutlet is being eliminated from the Interim Forested Depressional model nutrient cycling function because its effects are taken into account by FCIhydro.

 Soil Organic Matter (Vsoilom)

This variable represents the percentage of organic carbon in the upper soil profile. The organic content of soils has some significance for the retention of chemicals in a wetland. Mineral soils generally have lower cation exchange capacity than organic soils do; the former is dominated by various metal cations, and the latter is dominated by the hydrogen ion. Organic soils can therefore remove some contaminants (e.g. certain metals) through ion exchange and can enhance nitrogen removal by providing an energy source and anaerobic conditions appropriate for denitrification. Organic soil is composed primarily of the remains of plants in various stages of decomposition and accumulates in wetlands as a result of anaerobic conditions created by standing water or poorly drained conditions (Mitsch and Gosselink 1993). Almost all soils have a component of organic matter that influences into which textural class the soil falls. Since determining the percentage organic matter in a soil is a difficult prospect under typical field conditions, a surrogate is needed to help determine relative percentages for a given soil. The Field Indicators of Hydric Soils contains numerous indicators to help make hydric soil determinations, and several of these indicators are at least partially based upon the organic matter content of the soil (USDA 1996). For the purposes of this model, these indicators have been grouped into classes reflecting relative percentages of organic matter. See Appendix B for applicable indicators and the groupings. To apply this variable, it must be determined which of the indicators apply, and the following table is referenced to see what the variable scaling is. A more comprehensive approach would be to actually take a soil sample and determine organic matter content from soils test. The reference standard for organic matter will need to be determined for each subclass, with higher amounts (and therefore higher CEC’s) receiving lower scores as well as lower amounts.

Organic Hydric Soil Indicator Variable Index

Group 2 Indicator 1.0

Group 1 Indicator 0.7

Group 3 Indicator 0.5

Group 4, no organic indicator 0.3

Group 5, drained hydric soil 0.1

Group 6, non-hydric soil 0.0

 Detrital Matter (Vdm)

This variable represents the accumulation of non-woody dead plant material on the wetland soil surface available for breakdown by microbial action. Three measurements should be taken over the wetland assessment area and an average value used. This average value is entered into the following table to find the corresponding variable value.

Layer Thickness (inches) Variable Index

1/2 - 2 1.0

some - 1/2 or 2 - 4 0.5

none or > 4 0.1

converted site 0.0

Coarse Woody Debris (Vcwd)

This variable represents the accumulation of dead woody material (greater than 0.25 inches in diameter) which is available for nutrient cycling. For routine assessments, the number of pieces of woody debris on three 30 ft transects are estimated by size classes of 0.25-1.0 inches, 1.0-3.0 inches, and > 3 inches in diameter. The tally is recorded on the data sheet and multiplied by factors of 1.8 for the first size category, 12.0 for the second size category, and 923.6 for the third size category. The total volume is entered in the following table to find the corresponding variable value. For comprehensive assessments, the actual volume of the debris is calculated from the transect data (Trott et al).

Coarse Woody Debris Transect Number on Average Volume

Diameter 1 2 3 Transect

0.25 - 1.0 in. + + = X 1.8 = +

1.0 - 3.0 in. + + = X 12.0 = +

> 3.0 in. + + = X 923.6= =

Total Volume of Coarse Woody Debris = in3

Volume of Coarse Woody Debris Variable Index

******Estimates of woody debris needed******

2,500 - 10,000 1.0 Variable Index Scores

1,000 - 2499 or 10,001 - 15,000 0.5 are VERY rough estimates

0 - 999 or > 15,000 0.1

Not Restorable 0.0

 Surrounding Landuse (Vluse)

[formerly Loading of Dissolved Materials (Vdload)]

This variable represents the nutrient and compounds imported into the wetland attached to the suspended solid load and other compounds dissolved in runoff water. As the surrounding landuse becomes more intense, the amount of dissolved materials can be assumed to increase. This variable can be represented by the previously used Vluse. The Curve Number, which is used to calculate Vluse, is highly dependent upon the landuse. As the curve number increases (more intense landuse and more impervious surface), the runoff from the watershed increases. As the runoff increases, the erosion potential of the watershed increases and therefore the sediment load in the runoff increases. Also, as the surrounding landuse becomes more intense, the chemical and nutrient inputs to the watershed can be expected to become greater and the corresponding output of the watershed increase. Because of the expected relationship with the surrounding landuse, the previously described Vluse can be used as a simple surrogate for Vdload.

Weighted Curve Number Variable Index

less than 70 1.0

71 - 80 0.7

80 - 85 0.5

85 - 90 0.1

greater than 90 0.0

Clay Content (Vclay)

[ formerly Cation Exchange Capacity (Vcec)]

Cation exchange is the interchange between a cation in solution and another cation on the surface of any surface-active material. All soil components contribute, to some extent, to cation exchange sites; however, cation exchange in most soils is centered with clay and organic matter (Foth, 1984). CEC’s vary greatly depending on the mineralogy of the clay involved. However, by restricting the geographic variability of the model subclasses, the differences in the clay mineralogy should be minimized. So, in a given subclasses’ reference domain, the main differences in CEC (due to clay) should be based upon the quantity of clay in the soil. Because CEC is centered on more than just the clay (also organic matter), and the organic matter content of the soil is addressed in Vsoilom, this variable is being changed to Vclay. This should better reflect the fact that CEC is a combination of organic matter and clay. The routine assessment uses a weighted average of the clay content of the soil in the upper 20 inches. For non-soil scientist, this may be accomplished by texturing the soil layers according to figure F?? (texturing flow chart) and entering the resulting texture into figure F?? (textural triangle) to determine percent clay. Typically, the midpoint of the clay percentage is used unless the texture warrants using the high or low end of the clay percentage range. The percentage of clay is entered into graph G7 to determine the corresponding variable value. The reference standard percentage of clay will need to be determined for each subclass, with higher percentages of clay (and therefore higher CEC’s) receiving lower scores as well as lower percentages of clay.

This variable is being eliminated due to concerns about capturing natural variations rather than impacts to the wetland.

Water Acidity (VpH)

In the Florida Herbaceous Depressional model, this variable accounts for conditions within or around the watershed which could impact the water acidity, such as pumping from phosphate mines, which could alter the pH of the water in the wetland. This variable is being eliminated from the Interim Forested Depressional model because the major impact it was intended for does not apply to the reference domain and it appears that impacts will be dealt with in other variables, such as Vdload, Vssload, Vrunoff, and Vinlet.

 Soil Quality (Vsoilq)

This variable represents the physical integrity of the soil above the Bg or Btg horizon. This includes the number and continuity of pores and the type, grade, and size of soil structure. Measurement of soil condition will involve looking at roots, pores (abundance, size, and continuity), and soil friability (rupture resistance, from very friable to very friable and harder. Measurement is done on the more limiting part of the A horizon, directly above the Bg or Btg horizon. The Soil Quality Index (SQI) will be assigned for each of the three measured soil parameters. The points for each soil parameter will then be added. The Vsoilq index will be assigned based upon the total for the three soil parameters.

Pores: The quality and continuity of soil pores received a quantitative score of 1 through 3. Many fine and very fine pores in the A horizon receive a score of 3. Common pores receive a score of 2, and few pores a score of 1. Any deviation from the standard may be an indication that the site is not functioning to full capacity hydrologically. Less evidence of macropores indicates less water moving downward through the soil profile to recharge the water table. Nonmatrix and interstructural porosity have particular importance for water movement.

Consistence (Moisture): Consistence is now called "Rupture Resistance Classes for Block-like Specimens, slightly dry and wetter." Very friable and friable rupture resistance in the A horizon was indicated by a score of 3. Firm was indicated by a score of 2, and very firm or harder by a score of 1. This measure is an indication of compaction, which increases bulk density, which in turn reduces porosity.

Structure: Soil structure was rated according to the following metrics. Structure that was "Weak or moderate subangular blocky parting to moderate fine and medium subangular blocky parting to fine and medium granular" in the A horizon was noted by a score of 3. Fine to medium subangular blocky parting to granulate in the A horizon was scored as a 2. Massive or coarse subangular blocky or evidence of a plowpan were designated as a 1. A plowpan was indicated in the field by dense coarse, or massive, structure, and roots growing horizontally across the top of the pan.

Soil Quality Index Score Variable Index

greater than or equal to 7 1.0

4 - 6 0.5

less than or equal to 3 0.1

substrate is concrete, or non-porous 0.0

Material for this variable was provided by Leander Brown, NRCS Wetland Science Institute.

 Index of Function

FCIcycle =[ Vsoilom + (Vcwd + Vdm ) / 2 + (Vtree + Vshrub + Vgrndcvr) / 3 + Vluse + (Vsoilq + FCIhydro) / 2 ] / 5

 Particulate Retention

Definition: Retention of inorganic and organic particulates through physical processes. The function is measured in grams of particulates per square meter per year.

Discussion and Rational of Function: Particulates enter the wetland from the surrounding watershed. The source of the particulates is primarily erosion from the surrounding land. The addition to the wetland is primarily made up of soil particles, the attached nutrients, and any attached chemicals. Other sources include surrounding urban areas, industrial areas, and roads. The additions from these sources include soil particles, the associated nutrients and chemicals, grit from parking lots and roads, oil, etc. The amount of particulates retained in the wetland depends upon the amount entering the wetland and also whether or not a constructed outlet is present. A surrounding buffer can contribute to lower amounts of sediment reaching the wetland. The vegetated buffer causes runoff to slow, losing energy, which results in a portion of the sediment load dropping out before reaching the wetland.

Variable Descriptions:

Surrounding Landuse (Vluse)

[formerly Suspended Solid Load (Vssload)]

As the landuse in the contributing watershed of a wetland becomes more intense, a greater volume of suspended sediment, nutrients, and chemicals is expected to reach the wetland. The Curve Number, which is used to calculate Vluse, is highly dependent upon the landuse. As the curve number increases (more intense landuse and more impervious surface), the runoff from the watershed increases. As the runoff increases, the erosion potential of the watershed increases and therefore the sediment load in the runoff increases. Because of this relationship, the suspended solid load, Vssload, can be represented by the surrounding landuse, Vluse.

Weighted Curve Number Variable Index

less than 70 1.0

71 - 80 0.7

80 - 85 0.5

85 - 90 0.1

greater than 90 0.0

 Constructed Wetland Outlet (Voutlet)

This variable represents the effects of drainage on the depressional wetland, which alters both the hydroperiod and the hydrodynamics of the wetland. For routine assessments, this variable is a visual estimate of the alterations made to the depressional wetland, which is scaled in the following table. The comprehensive method is to calculate the extent of the drainage using hydrology tools (such as Kirkham’s equation for surface ponding and the van Schilfgaarde, Ellipse, or Hooghoudt equation for drainage ditches) (USDA 1997).

Drainage Impact Variable Index

No outlet or no modification to

natural outlet. 1.0

Outlet elevation lowered to significantly

reduce detention time of dynamic storage

but some static storage remains. 0.5

Outlet invert lowered to reduce dynamic

and static storage. 0.3

Outlet invert lowered to drain wetland 0.1

Wetland is drained and no restoration possible 0.0

 Constructed Wetland Inlet (Vinlet)

This variable represents changes to the hydrology of the depressional wetland due to structures adding water to the wetland from sources not naturally connected to the wetland. An example of this could be a drainage ditch which drains adjacent uplands and/or other nearby depressions which outlets into the depressional wetland. The routine assessment is a visual inventory of the structure(s) and the extent of the alteration which is scaled in the following table. The comprehensive method is to calculate the extend of the modification by use of standard hydraulics, i.e. Manning’s equation for a ditch.

Inlet Modification Variable Index

No inlet (point source) is present

or no modification to natural inlet. 1.0

Sufficient water is added to increase

static storage or enough natural flow is blocked

to reduce dynamic storage. 0.5

Sufficient water is added to significantly

increase static storage or enough natural

flow is blocked to reduce static storage. 0.1

Wetland is permanently flooded or

is cut of from water sources entirely. 0.0

 Vegetated Buffer (Vbuffer)

A vegetated buffer around a wetland can cause the suspended sediment load to drop out of runoff before entering the wetland area. The vegetation causes resistance to flow, increases Manning’s "n", and decreases the velocity of flow. This loss of energy causes the larger particles to settle out before reaching the wetland. Best Management Practices, BMP’s, and various conservation programs are increasingly recognizing vegetated buffers as being beneficial to wetlands as well as other surface waters.

Width of Buffer Variable Index

******Compare to BMP’s and Standards******

> 90% of wetland 75 - 89% 50 - 74% 25 - 49% < 25%

perimeter protected

> 100 feet and densely vegetated

so that concentrated flow is not occurring 1.0 0.7 0.5 0.3 0.1

35 - 100 feet and densely vegetated 0.7 0.5 0.3 0.1 0.0

20 - 35 feet and densely vegetated 0.5 0.3 0.1 0.0 0.0

< 20 feet and densely vegetated

or concentrated flow can occur

through buffer 0.3 0.1 0.0 0.0 0.0

No dense vegetated buffer, but vegetation 0.1 0.0 0.0 0.0 0.0

Developed around wetland (pavement etc.) 0.0 0.0 0.0 0.0 0.0

NOTE: If Vluse is 1.0, then Vbuffer also equals 1.0

Index of Function

FCIsed = (Vinlet + Voutlet + Vbuffer + Vluse) / 4

 Maintenance of Distribution and Abundance of Wildlife

Definition: The density and spatial distribution of wildlife (vertebrates and invertebrates) utilizing wetlands for food, cover, resting, reproduction, etc.

Discussion and Rational of Function: Wildlife use of depressional wetlands is dependent on a number of factors. The adjacent habitat support, or buffer, is critical because many species require a diversity of habitats to complete their life cycle. The ecological connectivity addresses barriers to wildlife migration and habitat fragmentation. The addition of exotic plant species, which can out-compete native species due to number of factors such hydrology degradation, resulting in major plant community shifts resulting in a significant change in wildlife use. Depressional wetlands are extremely important in providing breeding and foraging habitat for amphibians, and migratory birds.

The FL Herbaceous Depressional HGM Model focuses on whether a given depression is actually being used by wildlife and what trophic level that species is. It requires a wildlife survey or an actual sighting of a species. The SE Forested Depressions interim HGM method is relying on the concept "If you build it, they will come," or if the habitat structure is there, wildlife will utilize the site.

Variable Descriptions:

Ecosystem Connectivity (Veco)

This variable is defined as the measure of habitat fragmentation of the wetland relative to other wetlands and native plant communities. It identifies barriers to wildlife migration ranging from very small barriers such as unpaved roads and low-density housing to large hydrologic barriers such as regional canals and levied roads. Determine the location and type of barriers within 1 mile of the edge of the wetland using maps or aerial photography. To calculate, use the following formula:

Total Wetland Perimeter Score = Sum (% of wetland perimeter X barrier effectiveness rating) for each barrier category

A wetland with no ecological barriers would receive a subindex of 1.0. Those wetlands with some type of barrier, or some combination of barriers would receive an index less than 1.0. The value derived from the above equation is used directly into the function as the variable index (Trott et al).

Wildlife Barrier Barrier Effectiveness Rating

No Barrier 1.0

Small Barrier (unpaved roads,

low density housing, golf courses,

utility easements, railroads) 0.7

Moderate Barrier (2 lane paved road,

low dikes, moderate density housing,

residential golf courses) 0.3

Large Barrier (4 lane paved road,

parking lots, high density residential,

industrial and commercial development) 0.1

 Exotic Plant Species (Vexotic)

This variable is defined as the percent cover of aggressive exotic plant species (Appendix C for plant lists). Infestation of a wetland by exotic plant species crowds out native plant species which provide habitat and a food source for wildlife. It also frequently alters the number of strata, changes the hydroperiod and biogeochemical cycling functions of the wetland (Trott et al). The variable is assessed in the same manner as Vgrndcvr (or Vshrub or Vtree as appropriate) and the variable is scaled in the following table.

% Cover Exotics Variable Index

0 - 10 1.0

10 - 30 0.7

30 - 60 0.4

60 - 90 0.1

100 0.0

Surrounding Landuse (Vluse)

As the landuse in the contributing watershed of a wetland becomes more intense, a greater volume of suspended sediment, nutrients, and chemicals is expected to reach the wetland. The Curve Number, which is used to calculate Vluse, is highly dependent upon the landuse. The higher intensity landuses characterized by high composite curve numbers also should be of lower value for wildlife use. These higher intensity landuses include such things as commercial development, residential development, roads, cropping, and silvicultural activities.

Weighted Curve Number Variable Index

less than 70 1.0

71 - 80 0.7

80 - 85 0.5

85 - 90 0.1

greater than 90 0.0

If there is no contributing watershed for the wetland in question, and a value of 1 has been used for the other functions, calculate Vluse using a 1000 ft. radius around the depression. This value is to be used only for F4 Maintenance of Distribution and Abundance of Wildlife.

Vegetated Buffer (Vbuffer)

A vegetated buffer around a wetland can cause the suspended sediment load to drop out of runoff before entering the wetland area. The vegetation causes resistance to flow, increases Manning’s "n", and decreases the velocity of flow. This loss of energy causes the larger particles to settle out before reaching the wetland. Best Management Practices, BMP’s, and various conservation programs are increasingly recognizing vegetated buffers as being beneficial to wetlands as well as other surface waters.

Width of Buffer Variable Index

******Compare to BMP’s and Standards******

> 90% of wetland 75 - 89% 50 - 74% 25 - 49% < 25%

perimeter protected

> 100 feet and densely vegetated

so that concentrated flow is not occurring 1.0 0.7 0.5 0.3 0.1

35 - 100 feet and densely vegetated 0.7 0.5 0.3 0.1 0.0

20 - 35 feet and densely vegetated 0.5 0.3 0.1 0.0 0.0

< 20 feet and densely vegetated

or concentrated flow can occur

through buffer 0.3 0.1 0.0 0.0 0.0

No dense vegetated buffer, but vegetation 0.1 0.0 0.0 0.0 0.0

Developed around wetland (pavement etc.) 0.0 0.0 0.0 0.0 0.0

NOTE: If Vluse is 1.0, then Vbuffer also equals 1.0

 Vegetation Composition (Vcomp)

This variable is defined as the minimum percent of dominant species found on the site compared to the reference list of the tree layer, the shrub layer, or the herbaceous layer. The assessment is determine the dominant species in each stratum and comparing them to the reference list in Appendix C. Then the percent of occurrence is determined for each stratum. The lowest percent occurrence of the three stratum is then entered into the following table.

% Occurrence on Reference List Variable Index

75 - 100 1.0

45 - 74 0.6

20 - 44 0.3

< 20 0.1

Site Converted and no restoration possible 0.0

Canopy Regeneration (Vregen)

This variable is the density of saplings of the dominant canopy trees. This provides some measure of whether the site is self-maintaining. If the site has been drained or similarly impacted, the species in the sapling layer should be different (less hydrophytic) than the canopy layer. This variable should be the tree species between 10 - 20 feet tall and less than 4 inches in diameter. To be included in the count, the sapling species needs to occur on the reference species list in Appendix C. To scale this variable, determine the species of saplings, and the percentage of the species which occur on the reference species list.

Regeneration Variable Index

Vigorous stand of saplings and

>80 % of species occur on list 1.0

Saplings present and > 60% occur

on list 0.5

Few saplings and/or < 60% occur

on list 0.3

No sapling regeneration or

fewer than 40% occur on list 0.1

Site converted and no restoration possible 0.0

Index of Function

FCIwildlife = [ (Vluse + Veco + Vbuffer) / 3 + (Vexotic + Vregen + Vcomp) / 3 ] / 2

 Maintenance of Characteristic Plant Community

Definition: The typical species composition and biomass distribution of the vegetation. This function can be quantified as the species richness and abundance in each stratum of the native plant community.

Discussion and Rationale of Function: Plant species are characterized by the plant composition and distribution. Species composition is important because it reflects the environmental conditions of the wetland. Only species that are tolerant of the hydrology, soils, and other conditions can survive and grow in wetlands. Changes in the environment can lead to a shift in species composition.

Variable Descriptions:

Tree Cover (Vtree)

This variable is a surrogate for the amount of nutrients and compounds held in the tree layer, the amount of nutrients and compounds the tree layer takes up, and the nutrient cycling which occurs at any oxidized rhizospheres around the tree roots. For interim model purposes, Vtree should be estimated by the percent canopy cover of the tree layer and entered into the following table.

% Canopy Cover of Trees Variable Index

80 - 100 1.0

60 - 79 0.7

40 - 59 0.3

less than 40 0.1

Not restorable 0.0

Canopy Regeneration (Vregen)

This variable is the density of saplings of the dominant canopy trees. This provides some measure of whether the site is self-maintaining. If the site has been drained or similarly impacted, the species in the sapling layer should be different (less hydrophytic) than the canopy layer. This variable should be the tree species between 10 - 20 feet tall and less than 4 inches in diameter. To be included in the count, the sapling species needs to occur on the reference species list in Appendix C. To scale this variable, determine the species of saplings, and the percentage of the species which occur on the reference species list.

Regeneration Variable Index

Vigorous stand of saplings and

>80 % of species occur on list 1.0

Saplings present and > 60% occur

on list 0.5

Few saplings and/or < 60% occur

on list 0.3

No sapling regeneration or

fewer than 40% occur on list 0.1

Site converted and no restoration possible 0.0

 Shrub Density (Vshrub)

This variable is a surrogate for the amount of nutrients and compounds held in the shrub layer, the amount of nutrients and compounds the shrub layer takes up, and the nutrient cycling which occurs at any oxidized rhizospheres around shrub roots. For the routine assessment procedure, the percentage cover of the shrub layer is used. The comprehensive assessment is an actual count of the number of stems of woody vegetation greater than 3 feet tall, not falling into the tree class in a 0.01 acre plot (approximately 21 ft. X 21 ft. or approximately a 12 ft. radius circle) (Trott et al). The resulting value (for both procedures) is entered into the following table to find the corresponding variable value.

% Shrub Cover Variable Index

40 - 60 1.0

20 - 39 or 61 - 80 0.5

1 - 19 or 81 - 99 0.2

0 or 100 0.1

 Groundcover (Vgrndcvr)

This variable is a surrogate for the amount of nutrients and compounds held in the herbaceous layer, the amount of nutrients and compounds the herbaceous layer takes up, and the nutrient cycling which occurs at any oxidized rhizospheres around the roots. For the routine assessment procedure, the percent cover of the herbaceous layer is estimated. The comprehensive assessment is the percentage cover in a 1.1 yard2 plot (1meter2, or approximately 3.1 ft. X 3.1 ft.) (Trott et al). The resulting value (for both procedures) is entered into the following table to find the corresponding variable value.

% Herbaceous Groundcover Variable Index

20 - 40 1.0

1 - 19 or 41 - 60 0.5

0 or 61 - 80 0.2

81 - 100 0.1

Vegetation Composition (Vcomp)

This variable is defined as the minimum percent of dominant species found on the site compared to the reference list of the tree layer, the shrub layer, or the herbaceous layer (Trott et al). The assessment is determine the dominant species in each stratum and comparing them to the reference list in Appendix C. Then the percent of occurrence is determined for each stratum. The lowest percent occurrence of the three stratum is then entered into the following table.

% Occurrence on Reference List Variable Index

75 - 100 1.0

45 - 74 0.6

20 - 44 0.3

< 20 0.1

Site Converted and no restoration possible 0.0

Index of Function

FCIplant = [ Vcomp + Vregen + (Vtree + Vshrub + Vgrndcvr) / 3 + FCIhydro ] / 4

 Variable Usage in Functions

Functions

F1: Maintenance of Characteristic Hydrologic Regime

F2: Cycling of Nutrients and Compounds

F3: Particulate Retention

F4: Maintenance of Distribution and Abundance of Wildlife

F5: Maintenance of Characteristic Plant Community 

Variable

F1

F2

F3

F4

F5

Vbuffer    

X

X

 
Vcomp      

X

X

Vcwd  

X

     
Vdm  

X

     
Veco      

X

 
Vexotic      

X

 
Vgrndcvr  

X

   

X

Vinlet

X

 

X

   
Vluse

X

X

X

X

 
Voutlet

X

 

X

   
Vprofile

X

       
Vregen      

X

X

Vregion

X

       
Vshrub  

X

   

X

Vsoilom  

X

     
Vsoilq

X

X

     
Vtree

X

X

   

X

Vwshed

X

       

Appendix A

Curve Number material from TR-55 Material

 Appendix B

Hydric Soil Indicators from the Field Indicators of Hydric Soils

Groups of indicators based on relative percentages of organic carbon.

Group 1 Indicators

A1 Histosols

A2 Histic Epipedon

A3 Black Histic

F1 Loamy Mucky Mineral

Group 2 Indicators

S1 Sandy Mucky Mineral

A7 Mucky Mineral

A9 1cm Muck

Group 3 Indicators

S7 Dark Surface

A5 Stratified Layers

A6 Organic Bodies

 Appendix C

List of Dominant Vegetation to occur on the wetland site by stratum.

List of invasive exotic vegetation.

 GEORGIA

Exotics:

Chinaberry...Melia azebarach

Bahia Grass...Parodi notatum

Trees:

Oak...Quercus spp. Red Maple...Acer rubrum

Tupelo...Nyssa spp.

Shrubs:

Buttonbush...Cephalanthus spp. Highbush Blueberry...Vaccinium corymbosum

Wax Myrtle...Myrica spp. St. Johns- Wort...Hypericum spp.

 SOUTH CAROLINA

Trees:

Cypress...Taxodium spp. Sweetgum...Liquidamdar stiruciflua

Tupelo...Nyssa spp. Red Maple...Acer rubrum

Oak... Quercus spp. Red Bay...Persea borbonia

Sweetbay...Magnolia virgianan

Shrubs:

Sweet Pepperbush...Clethra spp.. Wax Myrtle...Myrica spp.

Fetterbush... Lyonia spp. Highbush Blueberry...Vaccinium corymbosum

Titi...Cyrilla racemiflora

Herbs:

Smartweed...Polygonum spp. Rushes...Juncus spp.

Sedges...Carex spp. Yellow-eyed Grass...Xyris spp.

Panicum...Panicum spp. Beakrush...Rhynchospora spp.

Meadow Beauty...Rhexia spp. Clubmoss...Lycopodium spp.

Flat Sedge...Cyperius spp.

 Literature Cited

Cowardin, Lewis M.; Carter, Virginia; Golet, Francis C.; and LaRoe, Edward T. Classification of Wetlands and Deepwater Habitats of the United States. United States Department of the Interior, Fish and Wildlife Service. Washington, DC.

Foth, Henry D. 1984. Fundamentals of Soil Science (seventh edition) New York, NY, John Wiley & Sons. pp 191.

Fretwell, J.D.; J.S. Williams; and P.J. Redman (compilers). 1996. National Water Summary On Wetland Resources. United States Geological Survey, Water Supply Paper 2425. pp. 7-14.

Mitsch, W.J., and J.G. Gosselink. 1993. Wetlands (second edition) New York, NY, Von Nostrand Reinhold. pp 100-102.

Trott, K.L., Davis, M.M., Grant, L.M., Beever, J.W., Evans, R.K., Gunsalus, B.E., Krupa, S.L., Noble, C.V., and Liudahl, K.J. (Field Test draft "Peninsular Florida Herbaceous Depressional Wetlands Hydrogeomorphic Depressional Wetlands Hydrogeomorphic (HGM) Regional Guidebook." U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS.

United States Department of Agriculture, Natural Resources Conservation Service. 1996. Field Indicators of Hydric Soils in the United States. G.W. Hurt, P.M. Whited, and Pringle, R.F. (eds,). USDA, NRCS, Fort Worth, TX. pp 5-9, 11, and 13.

United States Department of Agriculture, Natural Resources Conservation Service. 1997. National Engineering Field Handbook, Ch19, "Hydrology Tools for Wetland Determination". USDA, NRCS. pp 37-40.

United States Department of Agriculture, Soil Conservation Service. 1981. Agriculture Handbook 296, "Land Resource Regions and Major Land Resource Areas of the United States". USDA, SCS. Washington, DC. pp 95-96, 109, 111-112.

United States Department of Agriculture, Soil Conservation Service. 1986. Technical Release 55, "Urban Hydrology for Small Watersheds." USDA, SCS. pp 1-1, 2-1, 2-3, 2-5 to 2-8, and D-2.


OCTOBER 1997 - DRAFT

DECIDUOUS WETLAND FLATS MODEL

Variable Measurements

Vdrain

 

Zone Variable Index

1 0.1 ___________

2 0.5 score

3 1.0 V drain

 

[ ( _______ x 0.1) + ( _________ x 0.5) +(________ x 1.0) ] / _______

 

Vdrain= [ (Area Zone 1 x 0.1 ) + (Area Zone 2 x 0.5) + ( Area Zone 3 x 1.0 ) ] / total area

Vdam

 

Area Variable Index

1 - unaffected by impediment 1.0

2 - area upstream of impediment 0.1 ____________

3 - area of impediment 0.0 score

4 - area downstream of impediment 0.3 V dam

 

[ ( _______ x 1.0) + ( _________ x 0.1) + (________ x 0 ) + ( _______ x 0.3 ) ] / _______

 

Vdam = [ ( Area 1 x 1.0 ) + (Area 2 x 0.1 ) + ( Area 3 x 0 ) + ( Area 4 x 0.3 ) ] / total area

Vet

Cover Condition Variable Index

Relatively mature stands of vegetation (5 yrs +) 1.0

Agriculture use (crops/pasture) 0.3 _____________

Recent clearcut (< 5 years) 0.1 score

Impervious surface 0.0 V et

Vvol

Condition Variable Index

No fill OR excavation present 1.0 _____________

Fill OR excavation present 0.0 score

 

Vvol = [ 1.0 - ( area of impact / Area of wetland assessment site ) ] V vol

Vba ( tree greater than 6 " dbh )

Hardwood Basal Area Variable Index

> 125 ft2/ac 1.0

100 - 125 0.7 ____________

75 - 99 0.3 score

< 75 0.1

unrestorable 0.0 V ba

 

Vsoilq

Pores table Consistence table

Many fine and Very fine 3 Very friable and friable 3

Common 2 Firm 2

Few 1 Very firm or harder 1

Structure table

Weak or moderate subangular blocky

parting to moderate fine and medium

subangular blocky parting to fine and 3

medium granular Pores + Consistence + Structure = ____________

________+_______+________=_____________

Fine to medium subangular blocky Index

parting to granular 2

 

Massive or coarse subangular blocky

or plowpan 1

-----------------------------------------------------------------------------------------------------------------------------------------------------------------------

SQI Variable Index

Greater or equal to 7 1.0

4 -6 0.5 _____________

less or equal to 3 0.1 score

unrestorable 0.0 V soilq

V snag4

# 4" snags/acre Variable Index

> 19 1.0

12 -18 0.5

5 - 11 0.2 _____________

< 5 0.1 score

unrestorable 0.0 V snag4

V snag4 = Density of 4" snags = 43560 / (avg. distance) 2

Vcwd

CWD (ft3/ac) Variable Index

> 86 1.0

70 -85 0.7

55 - 69 0.5 _____________

40 - 54 0.2 score

< 40 0.1

unrestorable 0.0 V cwd

Vcwd = 15175 / ( avg. distance ) 2

Vregen (see list provided)

Regeneration Variable Index

Vigorous stand of saplings and

> 80% of species occur on list. 1.0

Some saplings present and > 60%

occur on list. 0.5

Few saplings and/or < 60%

occur on list. 0.3 ____________

score

Very few/no saplings and < 40%

occur on list. 0.1

unrestorable 0.0 V regen

Vmastpro

% of Vba that is hardmast producer Variable Index

Greater than 25% 1.0

15 - 25 0.7

10 - 14 0.5 _____________

less than 10 0.1 score

unrestorable 0.0 V mastpro

Vsnag8

# 8" in snags/acre Variable Index

Greater than 5 1.0

4 - 5 0.7

2 - 3 0.3 _____________

1 0.1 score

unrestorable 0.0 V snag8

Vsnag8 = 43560 / ( avg. distance) 2

 
Varea

Contiguous Wooded Area Variable Index

Greater than 500 acres 1.0

250 - 500 0.7 _____________

100 - 249 0.3 score

Less than 100 0.1 V area


Vlandpat

Landuse Category Variable Index

Category 1 1.0

Category 2 0.7 _____________

Category 3 0.3 score

Category 4 0.0 V landpat

Vlandpat = [ ( % Cat. 1 x 1.0 ) + ( % Cat. 2 x 0.5 ) + ( % Cat. 3 x 0.3 ) + ( % Cat. 4 x 0 ) ] / 100

 

FUNCTIONS

FCI hydro = minimum of ( V et + V soilq ) / 2 OR V drain OR V dam OR V vol

______________

(_________+_________) / 2 OR __________ OR _________OR___________ score

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

FCI cycle = ( Vsoilq + Vba + (Vsnag4 + Vcwd ) / 2 + FCI hydro ) / 4

 

_______+________+(_______+________) / 2 +___________) / 4 ______________

score

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

FCI habitat = ( Vba + Vregen + Vmastpro + Vsnag8 + Vcwd ) / 5

( __________+___________+__________+__________+____________ ) / 5 _______________

score

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -- - - -- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

 

FCI landscape = ( Vlandpat + Varea ) / 2

( ____________+_____________ ) / 2 _______________

score

 
OCTOBER 1997 - DRAFT

SOUTHEAST FORESTED DEPRESSIONAL MODEL

 

Variable Measurements

Vwshed

____________________ / ______________________ = _________________________

smaller # larger # Ratio

 

Size Ratio Variable Index

- 1.00 1.0

0.75- 0.89 0.7

0.50 - 0.74 0.5 __________

0.25 - 0.49 0.3 score

0.00 - 0.24 0.0 V wshed

Vluse (see curve number table)

Weighted Curve Number Variable Index

less than 70 1.0

71 - 80 0.7

80 -85 0.5 ___________

85 -90 0.1 score

greater than 90 0.0 V luse

 

Vprofile

% Wetland Volume Disturbed Variable Index

0 - 9 1.0

10 - 29 0.8

30 - 49 0.6 __________

50 -69 0.3 score

70 -100 0.1

unrestorable (paved) 0.0 V profile

Vtree

% Canopy Cover of Trees Variable Index

80 - 100 1.0

60 - 79 0.7

40 - 59 0.3 __________

less than 40 0.1 score

unrestorable 0.0 V tree

Vshrub

% Shrub Cover Variable Index

40 - 60 1.0

20 - 39 OR 61 -80 0.5

1 -19 OR 81 -99 0.2 __________

0 OR 100 0.1 score

unrestorable 0.0 V shrub

 

Vgrndcvr

% Herbaceous Groundcover Variable Index

20 -40 1.0

1 - 19 OR 41 -60 0.5

0 OR 61 -80 0.2 __________

81 -100 0.1 score

unrestorable 0.0 V grndcvr

 

Voutlet

Drainage Impact Variable Index

No outlet OR no modifications

to natural outlet. 1.0

 

Outlet elevation lowered to reduce

detention time of dynamic storage,

BUT some static storage remains. 0.5

__________

Outlet elevation lowered to significantly score

reduce dynamic AND static storage. 0.3

Wetland is drained. 0.1

Wetland is drained AND nonrestorable. 0.0 V outlet

 

Vinlet

Inlet Modification Variable Index

No inlet present (point source) OR

no modifications to natural inlet. 1.0

Sufficient water is added to increase

static storage OR sufficient natural flow

is blocked to reduce dynamic storage. 0.5

Sufficient water is added to significantly ____________

increase static storage OR sufficient water score

is blocked to reduce static storage. 0.1

 

Wetland is permanently flooded by structure

OR water source is completely blocked. 0.0 V inlet

Vregion (note: In most cases, this is 1.0)

Measure Variable Index

Wetland is not near a municipal

well or agricultural well. 1.0

Wetland is between 2,500 - 10,000 ft from

municipal well OR 1,000 - 5,000 ft from

a large agricultural well with known drawdown. 0.5

__________

Wetland is within 2,500 ft of a municipal well score

OR within 1,000 ft of a large agricultural well. 0.1

Hydrology removed because of drawdown. 0.0 V region

 
Vsoilom

Organic Hydric Soil Indicator Variable Index

Group 2 Indicator 1.0

Group 1 Indicator 0.7

Group 3 Indicator 0.5 _____________

No Organic Indicator 0.3 score

Drained Hydric Soil (Relic) 0.1

Non-Hydric soil 0.0 V soilom

 

Vdm

Layer Thickness (inches) Variable Index

- 2.0 1.0

- 0.5 OR 2.0 - 4.0 0.5 ____________

None OR > 4 0.1 score

Nonrestorable 0.0 V dm

Vcwd

Coarse Woody Debris (inches) Transect Number Average Volume

Diameter 1 2 3

- 1.0 _______+_______+_______=___________ x 1.8 = _____________ +

- 3.0 _______+_______+_______=___________ x 12.0 =_____________ +

> 3.0 ________+_______+_______=__________ x 923.6=______________ =

 

Total Volume of CWD = ________________________in3

 

Volume of CWD Variable Index

2,500 - 10,000 1.0

1,000 - 2499 OR 10,001 - 15,000 0.5 __________

0 - 999 OR > 15,000 0.1 score

Nonrestorable 0.0 V cwd

 

Vbuffer

Width of Buffer Variable Index

******Compare to BMP’s and Standards******

> 90% of wetland 75 - 89% 50 - 74% 25 - 49% < 25%

perimeter protected

> 100 feet and densely vegetated

so that concentrated flow is not occurring 1.0 0.7 0.5 0.3 0.1

35 - 100 feet and densely vegetated 0.7 0.5 0.3 0.1 0.0

20 - 35 feet and densely vegetated 0.5 0.3 0.1 0.0 0.0

< 20 feet and densely vegetated

or concentrated flow can occur

through buffer 0.3 0.1 0.0 0.0 0.0 _____________

score

No dense vegetated buffer, but vegetation 0.1 0.0 0.0 0.0 0.0

Developed around wetland (pavement etc.) 0.0 0.0 0.0 0.0 0.0 V buffer

NOTE: If Vluse is 1.0, then Vbuffer also equals 1.0

Veco

Wildlife Barrier Variable Index

No Barrier 1.0

Small Barrier (unpaved roads,

low density housing, golf courses,

utility easements, railroads, etc.) 0.7

Moderate Barrier (2 lane paved roads,

low dikes, moderate density housing,

residential golf courses, etc.) 0.3 ___________

score

Large Barrier (4 lane roads, highly

traveled 2 lane roads, parking lots, high

density residential, industrial and

commercial development, etc.) 0.1 V eco

Vexotics (see list provided)

% Cover Exotics Variable Index

< 10 1.0

10 - 30 0.7

30 -60 0.4 ___________

60 - 90 0.1 score

> 90 0.0 V exotics

Vregen (see list provided)

Regeneration Variable Index

Vigorous stand of saplings and

> 80% of species occur on list. 1.0

Some saplings present and > 60%

occur on list. 0.5

Few saplings and/or < 60%

occur on list. 0.3 ____________

score

Very few/none saplings and < 40%

occur on list. 0.1

unrestorable 0.0 V regen

 

Vcomp (see list provided)

% Occurrence on Reference List Variable Index

>75% 1.0

45 -75 0.6

20 -45 0.3 ____________

< 20% 0.1 score

unrestorable 0.0 V comp

_______________________________________________________________________________________________________

Plant List of WAA.

_____________________________________ ______________________________________

_____________________________________ _______________________________________

_____________________________________ _______________________________________

_____________________________________ _______________________________________

____________________________________ _______________________________________

____________________________________ _______________________________________

 

_____________________________ / __________________________________ = ________________________

# on plant list total # of plants on site % comp

Vsoilq

Pores SQI

Many fine and very fine (continuous) 3

Common (continuous and discontinuous) 2

Few (Discontinuous) 1

impervious 0

 

Consistence in the A Horizon SQI

Very friable or friable 3

Firm consistence 2

Very firm or harder consistence 1

 

Structure SQI

Weak or moderate subangularr blocky parting

to moderate fine and medium subangular blocky 3

parting to fine and fine medium granular

Fine to medium subangular blocky parting to granulate 2

Massive or coarse subangular blocky structure 1

 

Pores + Consistence + Structure = Value Index

 

_________+_________+_________=_______________

 

SQI Variable Index

> 7 1.0

4 - 6 0.5 _____________

 

< 3 0.1 score

impervious surface 0.0 V soilq

 FUNCTIONS

 

FCI hydro = use minimum of:

 

[ (Vluse + Vwshed) / 2 OR (Vprofile + Vtree + Vsoilq) / 3 OR Voutlet OR Vinlet OR Vregion ] ____________

score

_______ + ______ /2 or ( _______ + ______+______) / 3 or ______ ______ _______

 

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

 

FCI cycle =

[ Vsoilom + (Vcwd + Vdm) / 2 + (Vtree + Vshub + Vgrndcvr) / 3 + Vluse + (Vsoilq +FCIhydro) / 2] / 5 ____________

score

[________ +(_______+______) / 2 +( ______+______+_________) / 3 + _______+(_______+________) / 2 ] / 5

 

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

 

FCI sed =

(Vinlet + Voutlet + Vbuffer + Vluse) / 4 ____________

score

(______ + ______ + ______+_______) / 4

 

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

 

FCI wildlife =

[ (Vluse + Veco + Vbuffer) / 3 + (Vexotic + Vregen + Vcomp) / 3 ] / 2 ____________

score

[ _______+______+_______/ 3 + (_______+________+_______) / 3 ] / 2

 

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

 

FCI plant =

[ Vcomp + Vregen + (Vtree + Vshrub + Vgrndcvr) / 3 + FCIhydro ] / 4 ____________

score

[ _______+_______+(______+_______+_______) / 3 +________ ] / 4

 

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -