Using Soil Attributes for HGM Wetland Classification Richard Weber Wetland Hydraulic Engineer Wetland Team (Ret.) CNTSC, Fort Worth, TX Slide 1
Data Sources: Web Soil Survey County Scale Smaller than Reference Domain Pre-built Interpretations Geospatial Data Gateway Statewide Data Raster and Vector Larger than Reference Domain User Selected Interpretations MLRA Attribute Selection crunches an entire State s data Slide 2
Major Land Resource Areas GIS Layer Geospatial Data Gateway Slide 3
The Reference Domain The area within which a defined Subclass Exists Major Land Resource Area is a Good Default MLRA Subdivisions may Exist for Further Refinement Slide 4
Map Unit Polygons Also Occupy Landscape Positons in the Watershed SSURGO Geomorphic Descriptions are Useful, i.e.: Upland Drainageway Terrace Floodplain Depression Many, many others used Slide 5
Hydrologic Soil Group - HSG Developed ONLY for use to determine Runoff Curve Number (RCN) NRCS RCN Method HSG A, B, C, or D A Low runoff (think sponge) Low Runoff infers high recharge D High Runoff (think Duck s back) High Runoff infers low recharge Important in assessing wetland watershed Q: Is a watershed of HSG A or B soils likely to support Discharge Wetlands? HSG is in both WSS and SSURGO data Slide 6
Slope Class Soil Map Units have Slope Class Data Only Available in SSURGO Directly Applicable to Mineral Flats (0-2%) Willamette Valley, Oregon Wet Prairie (Tufted Hairgrass Provides Microtopography) Slide 7
Water Features WSS Provides Flooding, Ponding, and Groundwater Frequency and Duration by Month Quickly SSURGO requires user to access multiple tables, BUT more detail is available Flooding Lotic RIVERINE AND SLOPE Classes Ponding Lentic DEPRESSION, and Depressions in RIVERINE Slide 8
Taxonomy: Use With Care: Orders: Histosols ORGANIC FLATS and discharge sites like SLOPE and Discharge DEPRESSION Require near continuous saturation to form and maintain Entisols Young Soils like floodplains Suborders: Aquic (wet), Fluvic (water formed) Great Groups Includes Minerology Calcic indicates discharge Sub-Groups Available in both WSS and SSURGO Lack of evidence in the taxononomy does NOT mean absence of the attribute Slide 9 Presence of evidence in the name is more useful
Endo saturated and Epi saturated Great Groups: Use With Care: Endosaturated soils indicate Discharge Episaturated soils indicate Recharge Definition is depth of saturation down to 200 cm Not meant to be a hydrodynamic interp. Typical Episaturated wetlands: Episaturated RIVERINE, Recharge DEPRESSION, MINERAL FLAT Typical Endosaturated wetlands: SLOPE, Discharge DEPRESSION, Endosaturated RIVERINE Slide 10
Minerals and Great Groups Groundwater Dissolved Minerals At point of Discharge, ET leaves mineral concentrations behind Best Example is Calcium (calcic), ex: calciaquolls Horizonation - Bk Slide 11
Saturated Hydraulic Conductivity (Ksat) Function of: Texture Structure Bulk Density Others Increase in Ksat with Depth Indicates Vertical Downward Movement (Recharge) Recharge Wetlands MINERAL FLATS, Recharge DEPRESSIONS Episaturated RIVERINE Ex. Bt horizons Slide 12
Other Useful Soil Attributes from SSURGO: Geomorphic Description Drainage Class Slope Class Taxonomy Horizons Water Features Flooding Freq. and Dur. Ponding Freq. and Dur. Groundwater Depths Digital Elevation Data Can be used also to Aggregate and Dis-Aggregate Map Units Useful Database Tables: Component Map Unit Map Unit Aggregated Attributes (muaggat) Beyond our Scope Today Slide 13
Selection by Attributes SSURGO Vector Polygons Site or HUC-12 Scale Heads-up Mapping Red Calcareous Wet Prairie MINERAL FLAT Green Calcareous Marsh DEPRESSION Slide 14
HUC -12 Scale Large Enough to Display all HGM subclasses Small Enough to Visualize Floodplain Landscape Slide 15
RIVERINE ATTRIBUTES Geomorphic Descrition floodplain term Water Features Flooding means Lotic inundation Flood Frequency higher than Rarely RIVERINE Water Features can include Flooding, Ponding, and Groundwater all 3 Slide 16
RIVERINE Soil System Multiple HGM Sub-Classes Look for more geomorphic description detail Ex. Backswamps, Natural Levees, Oxbows on Floodplains Look for more Water Features. Ex. Ponding means it s a backswamp Slide 17
Problem! Stream Functions Vary with Scale 2 nd Order Kennebec 5 th Order Kennebec Map Unit Dis-Aggregation Slide 18
SLOPE Headwater Reaches Look for: High Water Table Histosols or Histic Epipedon Horizon Non-Floodplain geomorph (i.e. Upland Drainageways) No decrease in Ksat with Depth Slide 19
Landscape Functional Break: SLOPE to RIVERINE HGM Class Blue Ackmore Colo Complex, Endoaqolls, Upland Drainageways, WTD < 12 SLOPE Class Green Floodplains Slide 20
SLOPE Wetlands Watershed Reaches Above Floodplains Idaho Headwater Fen Kansas Headwater New York Headwater Fen Attributes: Taxonomy endosaturated Great Group Taxonony Histosol or Histic Geomorphic Description Ex. upland drainageways Water Features WTD < 12, most months Slide 21
DEPRESSION CLASS Nebraska Rainwater Basin Recharge DEPRESSION Wyoming Recharge DEPRESSION, Gillette South Carolina Carolina Bay Discharge DEPRESSION South Dakota Prairie Pothole Recharge DEPRESSION Slide 22
DEPRESSION - Recharge Horizonation Perching Layer. Look for Bt horizon Drastic decrease in Ksat with depth Slide 23
DEPRESSION - Discharge High Infiltration Uplands Support Strong Discharge Wetlands No perching layer Taxonomy Ex. Calcic subgroup Taxonomy Histosols or Histic Recharge Go > GI Discharge Gi > Go Flow Through Gi = Go Slide 24
MINERAL FLAT and DEPRESSION Brown MINERAL FLATS Interfluves (geomorphic desc.) 0-2% Slope Class Poorly Drained Also Decrease in Ksat with Depth Water Features no ponding, no flooding, only WTD < 12 Yellow DEPRESSION Depressions (geomorphic desc.) Ponding Frequency and Duration No Flooding Slide 25
Defining Landscape Ecological Function with the use of Hydrodynamic Vectors Slide 26
Hydrology Informed Wetland Classification Wetland sub-classes: Have a System Boundary Same Water Budget within the boundary Same Ecological Functions within the boundary Same Plant Community Same Maintenance Processes Same Response to Disturbance Same Management Prescriptions Same Soil Attributes Slide 27
Existing Landscape Classification Concepts Ecological Site Descriptions Starts with Plant Community States in Transition Driven by Disturbance Hydrogeomorphic (HGM) Landscape Classification Landscape and Hydrology Based Originally Developed for Wetland Functional Assessment Cooperative Soil Survey Mapping Driven by Landscape and Hydrologic Factors Slide 28
Tool for Wetland Definition Using Soils and Hydrology - Needs Simple Qualitative to Quantitative Translates to Spatial Mapping and Modeling Provides Visual Representation Uses Existing Soils Database Applies to all landscapes One-dimensional to three-dimensional Slide 29
Slide 30
Uplands (Interfluves) Indiana Flatwoods Nebraska Sandhills Prairie Pothole Region High Plains Colorado
Slide 32
Wet Interfluves- Mineral Flats < 1 acre Drainage Area WT < 12 Feeds Discharge Sites Delmarva Peninsula Slide 33
Slide 34
Moist Upland Sites Slide 35
Headwaters Utah Iowa Des Moines Lobe Idaho Panhandle Nebraska Sandhills
Losing Watershed Reaches NOT A WETLAND Slide 37
Wet Headwaters Boundary County, ID Slide 38
Groundwater Supply is increased with HSG A, B Soils Slide 39
Closed Recharge Depressions Prairie Potholes Slide 40
Slide 41
Closed Recharge Depressions and Wet Headwaters Slide 42
Slide 43
Landscape Definitions Vector Parameters Magnitude and Direction Runoff Runon Recharge Discharge Apply to Landforms: Watershed Elements Interfluves Headwaters Stream Corridors Slide 44
Jasper County, IA Brown Recharge/Discharge Mineral Flat Green Runon/Discharge Depression Blue Runon/Recharge/Discharge Headwater Yellow Runon/Runoff/Discharge Floodplain Slide 45
Questions? Wet Headwater Kansas Flint Hills photo: Jon Fripp
Thanks! Questions? Wetland HydrologyTechnical Note: Technical Note No. 3 - Soil Hydrodynamic Interpretations for Wetlands http://www.nrcs.usda.gov/wps/portal/ nrcs/main/national/water/wetlands/restore/ NRCS is an Equal Opportunity Slide 47 Employer and Provider