Use of airborne digital imagery to examine floodplain complexity at varying discharges Katelyn Driscoll Master’s Thesis Systems Ecology University of Montana Floodplains Remote Sensing
The relationship between discharge and floodplain complexity
Complexity = variation in geomorphic, hydrologic, and biological forms, functions, and linkages that exists among ecologically distinct elements of floodplain landscapes. • Geomorphological form
• Physical Processes
• Habitat Patches
• Primary Drivers
Stanford et al. 2005
Natural Flow Regime
• Streamflow = “Master Variable” • Flooding is part of the Natural Flow Regime of many rivers • Flood pulses are critical disturbances • Flow pulses below bankfull
Poff et al. 1997 • Connectivity = the exchange of matter, energy, and biota between different elements of the riverine landscape via the aqueous medium.
Amoros and Bornette, 2002 Whited et al. 2002 • Extreme Discharges
• Isolation vs. Inundation
Mosley, 1982
Hypothesis Floodplain complexity is maximized at intermediate discharges of a flooding event because small changes in flow result in substantial aquatic habitat changes and extreme discharges are associated with decreased habitat heterogeneity.
1. How do the areas of various floodplain habitats change from base flow to peak flow to base flow? 2. What patterns exist in the transitions made by floodplain habitats throughout the course of a flood event? 3. How do fluctuations in discharge influence habitat diversity of the floodplain, as well as dissimilarity in habitat composition?
• Identified 3 zones: Main Channel, Parafluvial, Orthofluvial • Power Analysis • 331 5x5 meter main channel plots • 1160 5x5 meter parafluvial plots • 350 50x50 meter orthofluvial plots • Hawth’s Analysis tool for ArcGIS to randomly select plots • Classified 21 habitat cover types • Stratified Random Sample with repeated measures design. • Limitations 1. How do the areas of various floodplain habitats change from base flow to peak flow to base flow? Main Channel Zone 8-Apr 8-May 21-May 27-May 2-Jul 5-Sep A AAAAA Backwater 3.28E+05 3.28E+05 3.29E+05 3.29E+05 3.29E+05 3.26E+05
BBBBBA Cobble 3.24E+05 3.56E+05 3.60E+05 3.56E+05 3.29E+05 2.46E+05
AAAAAA Pool 3.31E+05 3.25E+05 3.27E+05 3.26E+05 3.32E+05 3.31E+05
BBBABC Riffle 3.60E+05 3.23E+05 3.18E+05 2.55E+05 3.34E+05 3.81E+05
AAABAC Run 2.99E+05 2.84E+05 2.99E+05 3.70E+05 3.13E+05 4.06E+05
AAAAAARiffle Shadow 3.25E+05 3.41E+05 3.29E+05 3.19E+05 3.45E+05 3.12E+05
AAAAAA Shallow Shoreline 3.12E+05 3.38E+05 3.39E+05 3.45E+05 3.26E+05 3.11E+05
AAAAAA Springbrook 3.29E+05 3.28E+05 3.29E+05 3.29E+05 3.29E+05 3.26E+05
AAAAAA Vegetation 3.32E+05 3.37E+05 3.37E+05 3.34E+05 3.18E+05 3.13E+05
AAAAAA Wood Runs 3.26E+05 3.22E+05 3.29E+05 3.34E+05 3.30E+05 3.31E+05Cobble Main Channel Zone- Habitats That Did Not Change
Pools Springbrooks Vegetation
Shallow Shoreline Wood Backwaters Parafluvial Zone 8-Apr 8-May 21-May 27-May 2-Jul 5-Sep A A A A A A Backwater 4.02E+06 4.06E+06 4.07E+06 4.07E+06 3.99E+06 4.06E+06 B D E F C A Cobble 3.10E+06 4.57E+06 4.99E+06 5.56E+06 3.51E+06 2.54E+06 A A A A A A FC Pool 4.05E+06 4.03E+06 4.05E+06 4.05E+06 4.05E+06 4.05E+06 C AB C BC A D FC Riffle 4.17E+06 3.77E+06 4.11E+06 4.05E+06 3.68E+06 4.50E+06 B A B B B C FC Run 3.97E+06 3.66E+06 4.02E+06 4.01E+06 4.07E+06 4.54E+06 B A B B B B FC Shallow Shoreline 4.19E+06 3.66E+06 4.05E+06 4.14E+06 4.05E+06 4.18E+06 A B B C B C Herbaceous 3.46E+06 4.05E+06 3.88E+06 4.40E+06 3.94E+06 4.54E+06 A C B CD CD D MC Shallow Shoreline 3.48E+06 4.05E+06 3.76E+06 4.30E+06 4.22E+06 4.46E+06 B MainAB ChannelAB RifflesA B B Overbank Flow 4.13E+06 4.05E+06 4.07E+06 3.79E+06 4.11E+06 4.13E+06 A A A A A A Pond 3.99E+06 4.01E+06 4.09E+06 4.10E+06 4.03E+06 4.06E+06 A A A A A A MC Pool 4.08E+06 4.00E+06 4.03E+06 4.02E+06 4.07E+06 4.08E+06 D B B A C D Riffle 4.94E+06 3.85E+06 3.56E+06 2.55E+06 4.49E+06 4.88E+06 C B A C C C MC Run 4.55E+06 3.56E+06 3.03E+06 4.28E+06 4.35E+06 4.49E+06 CD BC AB D AB A Shadow 4.31E+06 4.08E+06 3.80E+06 4.42E+06 3.95E+06 3.70E+06 A A A A A A Springbrook 3.99E+06 3.99E+06 4.12E+06 4.19E+06 4.00E+06 3.98E+06 A A A A A A Wood Main Channel Runs 3.99E+06 3.99E+06 4.03E+06 4.06E+06 4.02E+06 4.15E+06 Cobble
8-Apr 8-May 21-May 27-May 2-Jul 5-Sep A A A A A A Backwater 4.02E+06 4.06E+06 4.07E+06 4.07E+06 3.99E+06 4.06E+06 B D E F C A Cobble 3.10E+06 4.57E+06 4.99E+06 5.56E+06 3.51E+06 2.54E+06 A A A A A A FC Pool 4.05E+06 4.03E+06 4.05E+06 4.05E+06 4.05E+06 4.05E+06 C AB C BC A D FC Riffle 4.17E+06 3.77E+06 4.11E+06 4.05E+06 3.68E+06 4.50E+06 B A B B B C FC Run 3.97E+06 3.66E+06 4.02E+06 4.01E+06 4.07E+06 4.54E+06 B A B B B B FC Shallow Shoreline 4.19E+06 3.66E+06 4.05E+06 4.14E+06 4.05E+06 4.18E+06 A B B C B C Herbaceous 3.46E+06 4.05E+06 3.88E+06 4.40E+06 3.94E+06 4.54E+06 A C B CD CD D MC Shallow Shoreline 3.48E+06 4.05E+06 3.76E+06 4.30E+06 4.22E+06 4.46E+06 B AB AB A B B Overbank Flow 4.13E+06 4.05E+06 4.07E+06 3.79E+06 4.11E+06 4.13E+06 A A A A A A Pond 3.99E+06 4.01E+06 4.09E+06 4.10E+06 4.03E+06 4.06E+06 A A A A A A MC Pool 4.08E+06 4.00E+06 4.03E+06 4.02E+06 4.07E+06 4.08E+06 D B B A C D Riffle 4.94E+06 3.85E+06 3.56E+06 2.55E+06 4.49E+06 4.88E+06 C B A C C C MC Run 4.55E+06 3.56E+06 3.03E+06 4.28E+06 4.35E+06 4.49E+06 CD BC AB D AB A Shadow 4.31E+06 4.08E+06 3.80E+06 4.42E+06 3.95E+06 3.70E+06 A A A A A A Springbrook 3.99E+06 3.99E+06 4.12E+06 4.19E+06 4.00E+06 3.98E+06 A A A A A A Wood 3.99E+06 3.99E+06 4.03E+06 4.06E+06 4.02E+06 4.15E+06
8-Apr 8-May 21-May 27-May 2-Jul 5-Sep A A A A A A Backwater 4.02E+06 4.06E+06 4.07E+06 4.07E+06 3.99E+06 4.06E+06 B D E F C A Cobble Parafluvial (Cont.) 3.10E+06 4.57E+06 4.99E+06 5.56E+06 3.51E+06 2.54E+06 A A A A A A FC Pool 4.05E+06 4.03E+06 4.05E+06 4.05E+06 4.05E+06 4.05E+06 C AB C BC A D FC Riffle 4.17E+06 3.77E+06 4.11E+06 4.05E+06 3.68E+06 4.50E+06 B A B B B C FC Run 3.97E+06 3.66E+06 4.02E+06 4.01E+06 4.07E+06 4.54E+06 B A B B B B FC Shallow Shoreline 4.19E+06 3.66E+06 4.05E+06 4.14E+06 4.05E+06 4.18E+06 A B B C B C Herbaceous 3.46E+06 4.05E+06 3.88E+06 4.40E+06 3.94E+06 4.54E+06 A C B CD CD D MC Shallow Shoreline Flood Channel Runs 3.48E+06 4.05E+06 3.76E+06 4.30E+06 4.22E+06 4.46E+06Flood Channel Riffles B AB AB A B B Overbank Flow 4.13E+06 4.05E+06 4.07E+06 3.79E+06 4.11E+06 4.13E+06 A A A A A A Pond 3.99E+06 4.01E+06 4.09E+06 4.10E+06 4.03E+06 4.06E+06 A A A A A A MC Pool 4.08E+06 4.00E+06 4.03E+06 4.02E+06 4.07E+06 4.08E+06 D B B A C D Riffle 4.94E+06 3.85E+06 3.56E+06 2.55E+06 4.49E+06 4.88E+06 C B A C C C MC Run 4.55E+06 3.56E+06 3.03E+06 4.28E+06 4.35E+06 4.49E+06 CD BC AB D AB A Shadow 4.31E+06 4.08E+06 3.80E+06 4.42E+06 3.95E+06 3.70E+06 A A A A A A Springbrook 3.99E+06 3.99E+06 4.12E+06 4.19E+06 4.00E+06 3.98E+06 A A A A A A Wood 3.99E+06 3.99E+06Overbank 4.03E+06 Flow 4.06E+06 4.02E+06 4.15E+06
Parafluvial Zone- Habitats That Did Not Change
Main Channel Pools Springbrooks Ponds
Flood Channel Pools Wood Backwaters Orthofluvial Zone 8-Apr 8-May 21-May 27-May 2-Jul 5-Sep AAAAAA Backwater 3.74E+05 3.74E+05 3.74E+05 3.74E+05 3.74E+05 3.72E+05
AB C C C BC A Cobble 3.34E+05 4.08E+05 4.09E+05 4.13E+05 3.71E+05 3.06E+05
AAAAAA FC Pool 3.73E+05 3.72E+05 3.72E+05 3.73E+05 3.73E+05 3.73E+05
B AB AB ABB FC Riffle 3.79E+05 3.52E+05 3.60E+05 3.51E+05 3.87E+05 4.14E+05
AAAA AB B FC Run 3.68E+05 3.56E+05 3.54E+05 3.57E+05 3.88E+05 4.19E+05
AAAAAA FC Shallow Shore 3.87E+05 3.70E+05 3.53E+05 3.68E+05 3.75E+05 3.91E+05
ABDCCB Ground 2.84E+05 3.46E+05 4.53E+05 4.17E+05 4.00E+05 3.42E+05
AAAAAA MC Pool 3.73E+05 3.73E+05 3.73E+05 3.73E+05 3.73E+05 3.73E+05
AAAAAA MC Riffle 3.81E+05 3.74E+05 3.75E+05 3.63E+05 3.69E+05 3.80E+05
AAAAAA MC Run 3.79E+05 3.71E+05 3.74E+05 3.73E+05 3.68E+05 3.77E+05
AAAAAA MC Shallow Shore 3.76E+05 3.75E+05 3.70E+05 3.75E+05 3.71E+05 3.75E+05
BBBABB Overbank Flood Channel Runs 4.02E+05 3.94E+05 3.65E+05 2.93E+05 3.84E+05 4.02E+05Flood Channel Riffles AAAAAA Pond 3.78E+05 3.66E+05 3.74E+05 3.74E+05 3.67E+05 3.84E+05
AAAAAA Springbrook 3.87E+05 3.72E+05 3.64E+05 3.63E+05 3.78E+05 3.78E+05
AAAAAA Vegetation 3.73E+05 3.73E+05 3.73E+05 3.73E+05 3.72E+05 3.73E+05
A C BC C C AB Wood 3.12E+05 4.69E+05 3.62E+05 3.75E+05 3.77E+05 3.36E+05 8-Apr 8-May 21-May 27-May 2-Jul 5-Sep AAAAAA Backwater 3.74E+05 3.74E+05 3.74E+05 3.74E+05 3.74E+05 3.72E+05
AB C C C BC A Cobble 3.34E+05 4.08E+05 4.09E+05 4.13E+05 3.71E+05 3.06E+05
AAAAAA FC Pool 3.73E+05 3.72E+05 3.72E+05 3.73E+05 3.73E+05 3.73E+05
B AB AB ABB FC Riffle 3.79E+05 3.52E+05 3.60E+05 3.51E+05 3.87E+05 4.14E+05
AAAA AB B FC Run 3.68E+05 3.56E+05 3.54E+05 3.57E+05 3.88E+05 4.19E+05
AAAAAA FC Shallow Shore 3.87E+05 3.70E+05 3.53E+05 3.68E+05 3.75E+05 3.91E+05
ABDCCB Ground 2.84E+05 3.46E+05 4.53E+05 4.17E+05 4.00E+05 3.42E+05
AAAAAA MC Pool 3.73E+05 3.73E+05Cobble 3.73E+05 3.73E+05 3.73E+05 3.73E+05
AAAAAA MC Riffle 3.81E+05 3.74E+05 3.75E+05 3.63E+05 3.69E+05 3.80E+05
AAAAAA MC Run 3.79E+05 3.71E+05 3.74E+05 3.73E+05 3.68E+05 3.77E+05
AAAAAA MC Shallow Shore 3.76E+05 3.75E+05 3.70E+05 3.75E+05 3.71E+05 3.75E+05
BBBABB Overbank 4.02E+05 3.94E+05 3.65E+05 2.93E+05 3.84E+05 4.02E+05
AAAAAA Pond 3.78E+05 3.66E+05 3.74E+05 3.74E+05 3.67E+05 3.84E+05
AAAAAA Springbrook 3.87E+05 3.72E+05 3.64E+05 3.63E+05 3.78E+05 3.78E+05
AAAAAA Vegetation 3.73E+05 3.73E+05 3.73E+05 3.73E+05 3.72E+05 3.73E+05
A C BC C C AB Wood Overbank Flow 3.12E+05 4.69E+05 3.62E+05 3.75E+05 3.77E+05 3.36E+05 Wood Orthofluvial Zone -Habitats That Did Not Change
Cottonwoods & Conifers
Main & Flood Channel Shallow Springbrooks Shorelines
Backwaters Flood Channel Pools Ponds Summary • Riffles and Runs were the most dominant habitat in primary and secondary channels • Riffles expanded and contracted and runs generally remained constant, indicating that as flow spreads throughout the floodplain the newly formed habitat is most often riffle.
• The areal abundance of backwaters, pools, springbrooks and ponds did not significantly change during the study period in any zone, suggesting the area of these habitats is either unaffected by fluctuations in discharge or they have short lifespans. 2. What patterns exist in the transitions made by floodplain habitats throughout the course of a flood event? Main Channel Parafluvial Zone Orthofluvial Zone Summary
• Shadows affected the classification of habitats
• Transitions in the Main Channel suggest a channel shift
• Main Channel and Parafluvial transitions are indicative of succession
• The Orthofluvial Zone is dominated by the herbaceous cover type and aquatic habitats make up a small proportion of the landscape 3. How do fluctuations in discharge influence habitat diversity of the floodplain, as well as dissimilarity in habitat composition?
Main Channel Parafluvial Orthofluvial Summary
• Habitats that occupy small and statistically insignificant areas on the floodplain play a role in habitat diversity • The high diversity of the parafluvial zone reflects its close proximity to the main channel, displaying both main channel and off channel habitats • Alpha Diversity within each zone does not significantly differ at different flows, but habitat dissimilarity is associated with fluctuations in discharge. • The Parafluvial Zone is the most diverse, followed by the Orthofluvial zone. The main channel is the least diverse.
Floodplain complexity is maximized at intermediate discharges of a flooding event because small changes in flow result in substantial aquatic habitat changes and extreme discharges are associated with decreased habitat heterogeneity.
1. How do the areas of various floodplain habitats change from base flow to peak flow to base flow? 2. What patterns exist in the transitions made by floodplain habitats throughout the course of a flood event? 3. How do fluctuations in discharge influence habitat diversity of the floodplain, as well as dissimilarity in habitat composition? Conclusions • Observed a relationship between discharge and floodplain complexity through a flood pulse. • Diverse habitats were created and destroyed throughout the snowmelt event, directly affecting habitat heterogeneity at different flows. • Three zones evolve, providing different habitat cover types at each discharge • Maximized complexity during intermediate discharges is manifested in the parafluvial zone • Underscores the importance of natural flow regimes, how timing, magnitude, frequency, and duration of a flooding event impact complexity • Understanding the link between discharge and floodplain structure is critical as natural flow regimes are increasingly threatened by diversions, regulation, and climate change. Acknowledgements • My Advisor • cDr. Ri Hauer • My Committee • Dr. Maury Valett • Dr. Libby Metcalf This research is being supported by • Dr. Lloyd Queen the National Science Foundation • Andrew Hauer, Phil Matson, Dr. EPSCoR program to the State of Marc Peipoch Montana and through the Montana Institute on Ecosystems Questions?