USING HYDROLOGY TO COMPARE A REGIONAL HYDROGEOMORPHIC (HGM)
CLASSIFICATION ACROSS A LATITUDINAL GRADIENT OF THE APPALACHIAN
MOUNTAINS
Charles Andrew Cole - Penn State UniversityChris Cirmo - SUNY, Cortland
Denise Wardrop - Penn State UniversityRobert P. Brooks - Penn State UniversityJessica Peterson – Penn State University
Riparian Depressions
NY
PA
VA
1997 HGM key for the Ridge and Valley
• A quick means of identifying HGM subclass• A direct way into the assessment of function• May or may not work anywhere else along the
Appalachian Mountains
• Objective: Use hydrology to assess HGM key north and south along Appalachian Mountains
Hydrogeomorphology
Depression
Slope
Floodplain
Fringing
Flats
Impoundment
Reference Wetlands
• Group of natural wetlands w/in a region
• ‘Pristine’ to disturbed• Used to develop
range of expected conditions
• Problems include:• Lack of good data• Hard to get good data• Need landscape
component• Relationship between
functions and values?
Riparian Depression
• Adjacent to streams
• Surface outlet with unidirectional flow
• No water from overbank flooding
• Soils saturated, rarely flooded
• Low energy systems
• PEM, PSS, PFO
Slope
• On topographic gradient
• Surface and groundwater
• Saturated, rarely inundated
• Low energy systems• PEM, PSS, PFO
Headwater floodplain
• Adjacent to 1st, 2nd order streams
• Not much overbank flooding. Overland flow, groundwater
• Saturation. Often dry
• Low to high energy
• Frequently PFO, PSS
Hydrology
RDS WL40’s and Ecotones
Headwater floodplains Slopes
Riparian depressions
1=PA2=NY – AD3=NY – Cat4=VA
1 2
3
4
4321
0
-10
-20
Region
Med
ian
of
Dep
th
Median depth (cm) – headwater floodplain
PA NY-A NY-C VA
(Kruskal Wallis H=5501.1, df=3, p<0.000)
1 2
3
4
4321
0
-10
-20
Region
Med
ian
of
Dep
th
Median depth (cm) – slope
PA NY-A NY-C VA
(Kruskal Wallis H=20425.21, df = 3,P< 0.001)
Median depth (cm) – riparian depression
PA NY-A NY-C VA
1 2
3
4
4321
0
-10
-20
Region
Med
ian
of
Dep
th
(Kruskal Wallis H=2688.20, df=3, p<0.001)
1 2
3
4
4321
0
-10
-20
Region
Med
ian
of
Dep
th
1 2
3
4
4321
0
-10
-20
Region
Med
ian
of
Dep
th
1 2
3
4
4321
0
-10
-20
Region
Med
ian
of
Dep
th
Headwater floodplain
Slope
Riparian depression
Wet and dry periods – by HGM subclass
And the reason is….
Credit: David Westphalen/Painet Inc.
• New York wetlands were substantially impacted by beaver
• Hard to find any site that was not modified by a beaver
• Really altered the duration of wet periods (though not dry periods)
• Reduced fluctuations
• We will need to revamp the HGM classification
• Works well south … other locations depend on beavers?
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