Introduction to the Hydrogeomorphic (HGM) Classification System

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 Slope Puerto Rico Depressional Carolina Bay Estuarine Fringe Oregon Mineral Flats Indiana Flatwoods

Reference Domains - Major Land Resource Areas Slide 6 Site Concept Valid Within MLRA Extent (or subdivision of MLRA)

HUC-12 in MLRA 103 Northeast Kansas Slide 7 Headwater HUC Similar to other Headwater HUC in MLRA 103 Reference Domain

Same Map Units Correlate to Similar Sub-Classes in Slide 8 Adjacent HUCS (Same MLRA) Floodplain Landscape

Landscape Boundaries - RIVERINE Slide 9 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

RIVERINE Wetlands Landscape Position: Soils Geomorphic Description - Floodplain

RIVERINE Dominant Water Slide Source Stream Hydrograph 12 Soil Water Features Flooding Ponding Groundwater Hydroperiod

RIVERINE Surface Flooding (Lotic) Slide 13

RIVERINE Ponding (Lentic) Slide 14

RIVERINE Floodplain Groundwater Slide 15

How Many Sub- Classes? Slide 16 Active Channel: Flooding Natural Levee: Non-wetland Backswamp: Groundwater Upland: Non-wetland

RIVERINE Landscapes Can have Multiple HGM Sub-Classes Unique: Landform Plant Community Groundwater Table Flood Frequency Flood Duration Ponding Potential Soil

Introducing - Endosaturated Riverine Tongue River, Wyoming Ninnescah River, Kansas Saturated from Below USDA NRCS Module Name 18

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 Groundwater Rises and Falls with the Stream Water Surface USDA NRCS Module Name 19

Introducing - Episaturated Riverine Iowa photo: NRCS Photo Gallery USDA NRCS Module Name 20

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 21

RIVERINE Ponded Backswamp Hydric (Floodplain Oxbow) Partiallly Hydric (Floodplain Flat) Active Channel RIVERINE, Backswamp, episaturated herbaceous In MLRA 73 USDA NRCS Module Name 22

RIVERINE Morphology - Natural Levees Backswamps Verdigris Series Partially Hydric Natural Levee Osage Series Hydric Backswamp Slide 23

SLOPE Dominant Water Source Groundwater Discharge Slide 24

SLOPE Landscape Position Concave Topographic positions, usually stream headwaters Slide 25

Topographic SLOPE Wetland Plan View Concave Landscape Positions Typical of Stream Headwaters Slide 26

Topographic SLOPE Cross-Section Deep Discharge Shown Here Often is Shallow Subsurface Flow in Soil

Potential Bog Turtle Habitat Typic Endoaquults Groundwater Dominated Soils In Low Stream Order Landscapes SLOPE, Headwater Slide 28

SLOPE Wetlands Idaho Headwater Fen Kansas Headwater New York Headwater Fen Fens SLOPE Class Near continuous discharge Organic Soil Slide 29

Slope HGM Class Wetland Wyoming (Sage Grouse Country) Slide 30

SLOPE Wetland Before Restoration Surface Saturated Groundwater Fed Large Scale Not Flooded Not Ponded Slide 31

SLOPE Wetland After Restoration Lowered Groundwater Aerated Organic Soil Lateral Effect of Constructed Stream Restoration Loss of Wetland Hydrology Slide 32

To Drain a SLOPE Wetland - Finger Lakes Region, NY Groundwater From Uplands Simply Plug the Ditch Restores Groundwater Discharge Intercept Groundwater at Point of Discharge USDA NRCS Module Name 33

OR Install a Drainage Ditch Through It Groundwater Discharge Des Moines Lobe, Iowa USDA NRCS Module Name 34

OR Allow a Gully to Form Through It Nebraska Sand Hills Formerly Saturated Surface Upstream Dam has Captured Sediment Current Groundwater Discharge Level Aerated Organic Soil USDA NRCS Module Name 35

MINERAL SOIL FLAT Dominant Water Source- Direct Precipitation Landscape Position Interfluves Low Flow Accumulation Depressions may be embedded within Mineral Flats Slide 36

MINERAL FLAT Wetland Hydrodynamics Vertical, Downward Dominant Water Source - Precipitation Slide 37

Mineral Flat Extent Map 0-2% Slopes Poorly Drained to Very Poorly Drained Decrease in Ksat with Depth Perched Water Table Slide 38

ORGANIC SOIL FLAT Dominant Water Source Direct Precipitation Ombotrophic Bogs Pocosins Pocosin North Carolina Slide 39

ESTUARINE FRINGE Dominant Water Source - Tides Slide 40

Estuarine Fringe Organic Soils are Common Tidally Influenced Salt, Brackish, or Freshwater Adjoins Riverine HGM landscapes Slide 41

ESTUARINE FRINGE Tidal Inlet Channels Slide 42

LACUSTRINE FRINGE Dominant Water Source- Lake Fluctuations Yellowstone Lake, Wyoming Horizontal, bi-directional Slide 43

DEPRESSIONAL Closed Topographic Depressions Nebraska Rainwater Basin Recharge Depression Wyoming Recharge Depression, Gillette South Dakota Prairie Pothole South Carolina Carolina Bay Slide 44

DEPRESSIONAL Dominant Water Source Surface Runoff and/or Groundwater Slide 45

Depressional Recharge Slide 46

Depressional Discharge or Flow Through Recharge G o > G i Discharge G i > G o Flow Through G i = G o Slide 47

DEPRESSIONS Web Soil Survey Map Units South Dakota Prairie Potholes Recharge, Discharge, and Flowthrough Texas Playas Recharge Randall Clay Slide 48

Generalized Landscape Map Slide 49

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 Slide 50

Questions? Kansas Flint Hills photo: Jon Fripp