Hydrogeomorphic Functional Assessment Models – Headwater ...
Introduction to the Hydrogeomorphic (HGM) Classification ... · Introduction to the Hydrogeomorphic...
Transcript of Introduction to the Hydrogeomorphic (HGM) Classification ... · Introduction to the Hydrogeomorphic...
Introduction to the Hydrogeomorphic (HGM) Classification System
Objectives – The Student Will be Able to:
• Define the 7 HGM Classes • List the 3 Parameters That Define HGM
Classes • List the Major Water Budget Components for
Each Class • Select Appropriate Local Reference Domains • Determine Useful Local HGM Sub-classes • Relate HGM Sub-Classes to Soils • Ready to Learn how to Select the Appropriate
Analysis Technique for Sub-Classes
HGM
•Originally for Development of “Functional Assessment Models” (Brinson, et. al.) •Starts with 7 Wetland Classes •Requires the Determination of a “Reference Domain” where a certain “subclass” exists •Must make a decision between “lumping” and “splitting”
Three Factors that Define Wetland Classes •Landscape Position •Dominant Water Source •Hydrodynamics
The Seven HGM Classes
•RIVERINE •SLOPE •MINERAL SOIL FLAT •ORGANIC SOIL FLAT •ESTUARINE FRINGE •LACUSTRINE FRINGE •DEPRESSION
Mineral Flats Indiana Flatwoods
Slope Puerto Rico
Depressional Carolina Bay
Estuarine Fringe Oregon
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Reference Domains - Major Land Resource Areas
Site Concept Valid Within MLRA Extent (or subdivision of MLRA)
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HUC-12 in MLRA 103 Northeast Kansas
• “Headwater” HUC • Similar to other Headwater
HUC in MLRA 103 “Reference Domain”
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Same Map Units Correlate to Similar Sub-Classes in Adjacent HUCS (Same MLRA)
Floodplain Landscape
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Landscape Boundaries - RIVERINE
Wabash Occasionally Flooded Poorly Drained Backswamp?
Kennebec Moderately Well Drained Occasionally Flooded Natural Levee?
RIVERINE Wetlands
Landscape Position Floodplains Dominant Water Source Surface Flooding AND/OR Groundwater Inputs Hydrodynamics Horizontal, Bi-Directional
Floodplain Oxbow -Wyoming
Landscape Position:
RIVERINE Wetlands
Soils Geomorphic Description - “Floodplain”
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RIVERINE – Dominant Water Source – Stream Hydrograph Soil “Water Features” •Flooding •Ponding •Groundwater Hydroperiod
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RIVERINE – Surface Flooding (Lotic)
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RIVERINE – Ponding (Lentic)
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RIVERINE – Floodplain Groundwater
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How Many Sub-Classes?
Upland: Non-wetland
Natural Levee: Non-wetland
Backswamp: Groundwater
Active Channel: Flooding
RIVERINE Landscapes Can have Multiple HGM Sub-Classes
Unique: • Landform • Plant Community • Groundwater Table • Flood Frequency • Flood Duration • Ponding Potential • Soil
USDA | NRCS | Module Name 18
Introducing - Endosaturated Riverine
Ninnescah River, Kansas
Tongue River, Wyoming
“Saturated from Below”
USDA | NRCS | Module Name 19
Groundwater Rises and Falls with the Stream Water Surface
Endosaturated Riverine Features • High Ksat Floodplains (Sands
Gravels) • Wet from high groundwater • Attenuated hydrographs • Strong Baseflow in channel • Surface Flooding not needed to
create wetland hydrology
• High groundwater • No ponding • Flooding need not
be long duration or high frequency for ecological function
USDA | NRCS | Module Name 20
Introducing - Episaturated Riverine
Iowa photo: NRCS Photo Gallery
USDA | NRCS | Module Name 21
Episaturated Riverine Features • Low Ksat Floodplains (Silts and
Clays) • Weak Connection between
stream water surface and floodplain Groundwater level
• Wet when inundated or ponded only
• Perched groundwater
• Ponding in backswamps
• Frequency and Duration of Flooding critical for ecological functions
RIVERINE, Backswamp, episaturated herbaceous
USDA | NRCS | Module Name 22
RIVERINE – Ponded Backswamp
Hydric (Floodplain Oxbow)
Partiallly Hydric (Floodplain Flat)
Active Channel
RIVERINE, Backswamp, episaturated herbaceous In MLRA 73
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RIVERINE Morphology - •Natural Levees •Backswamps
Osage Series •Hydric •Backswamp
Verdigris Series •Partially Hydric •Natural Levee
SLOPE
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Dominant Water Source – Groundwater Discharge
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SLOPE
Landscape Position – Concave Topographic positions, usually stream headwaters –
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Topographic SLOPE Wetland Plan View Concave Landscape Positions Typical of Stream Headwaters
Topographic SLOPE Cross-Section • “Deep”
Discharge Shown Here
• Often is Shallow Subsurface Flow in Soil
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Potential Bog Turtle Habitat “Typic Endoaquults” Groundwater Dominated Soils In Low Stream Order Landscapes
SLOPE, Headwater
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SLOPE Wetlands
Kansas Headwater
Idaho Headwater Fen
New York Headwater Fen
Fens • SLOPE Class • Near continuous discharge • Organic Soil
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Slope HGM Class Wetland Wyoming (Sage Grouse Country)
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SLOPE Wetland Before “Restoration”
• Surface Saturated • Groundwater Fed • Large Scale • Not “Flooded” • Not “Ponded”
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SLOPE Wetland After “Restoration”
• Lowered Groundwater • Aerated Organic Soil • Lateral Effect of Constructed “Stream Restoration” • Loss of Wetland Hydrology
USDA | NRCS | Module Name 33
To Drain a SLOPE Wetland -
Groundwater From Uplands
Intercept Groundwater at Point of Discharge
Finger Lakes Region, NY
Simply Plug the Ditch – Restores Groundwater Discharge
USDA | NRCS | Module Name 34
OR – Install a Drainage Ditch Through It
Des Moines Lobe, Iowa
Groundwater Discharge
USDA | NRCS | Module Name 35
OR – Allow a Gully to Form Through It
Current Groundwater Discharge Level
Aerated Organic Soil
Formerly Saturated Surface Upstream Dam has Captured Sediment
Nebraska Sand Hills
MINERAL SOIL FLAT Dominant Water Source- Direct Precipitation
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• Landscape Position – Interfluves • Low Flow Accumulation • Depressions may be embedded within Mineral Flats
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MINERAL FLAT Wetland Hydrodynamics – Vertical, Downward
• Dominant Water Source - Precipitation
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• 0-2% Slopes • Poorly Drained to
Very Poorly Drained • Decrease in Ksat
with Depth • Perched Water
Table
Mineral Flat Extent Map
ORGANIC SOIL FLAT Dominant Water Source – Direct Precipitation
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Pocosin – North Carolina
•Ombotrophic •“Bogs” •“Pocosins”
ESTUARINE FRINGE Dominant Water Source - Tides
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Estuarine Fringe •Organic Soils are Common
•Tidally Influenced Salt, Brackish, or Freshwater
•Adjoins Riverine HGM landscapes
ESTUARINE FRINGE – Tidal Inlet Channels
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Yellowstone Lake, Wyoming
Horizontal, bi-directional
LACUSTRINE FRINGE Dominant Water Source- Lake Fluctuations
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Nebraska Rainwater Basin – Recharge Depression
Wyoming – Recharge Depression, Gillette
South Dakota Prairie Pothole
South Carolina – Carolina Bay
DEPRESSIONAL Closed Topographic Depressions
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DEPRESSIONAL Dominant Water Source – Surface Runoff and/or Groundwater
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Depressional – Recharge
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Depressional – Discharge or Flow Through
Recharge Go > Gi Discharge Gi > Go Flow Through Gi = Go
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Texas Playas – Recharge Randall Clay
South Dakota Prairie Potholes – Recharge, Discharge, and Flowthrough
DEPRESSIONS Web Soil Survey Map Units
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Generalized Landscape Map
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HGM Parameters
The Hydrogeomorphic (HGM) Classification System is based on 3 factors – •Landscape Position
•WHERE it is •Dominant Water Source
•Not the ONLY Source •Hydrodynamics
•The direction(s) of water movement in and out
Questions?
Kansas Flint Hills photo: Jon Fripp