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Big Cypress/Caddo Watershed Geomorphic Classification. Ryan Smith The Nature Conservancy of Texas. Utility of River Classification. Understand watershed context of the river Understand normal channel, habitat, and biological characteristics Understand impacts on natural characteristics
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Big Cypress/Caddo WatershedGeomorphic Classification Ryan Smith The Nature Conservancy of Texas
Utility of River Classification • Understand watershed context of the river • Understand normal channel, habitat, and biological characteristics • Understand impacts on natural characteristics • Selection of reaches for studies of habitat, water quality, riparian, etc
River Styles • Brierly and Fryirs 2000 • Developed in Australia • Selected by TCEQ, TPWD, and TWDB for Texas Instream Flows Program • Meets recommendations of NAS review • Physical basis • Channel morphology • Hierarchical structure • Physiographic/hydrologic setting • Floodplain and riparian zone
Stages of a River Styles Procedure Stage 1 Data Compilation (description and mapping) •Derive watershed boundary conditions •Determine landscape units •Assess river character Stage 2 Data Analysis •Define and interpret River Styles •Explain contemporary character/behavior •Assess river history Stage 3 Predict future river structure Stage 4 Prioritize watershed management issues Stage 5 Identify target conditions for river
Watershed area determined by drainage divide. Determines the boundary conditions within which rivers operate. Watershed Topographic unit determined on the basis of local relief, valley slope and morphology. Defines the valley-setting. Landscape Unit Length of channel with a characteristic assemblage of geomorphic units. River Style Instream and floodplain landforms (pools, bars, levees, backwaters, etc.) that reflect distinct form-process associations. Geomorphic Unit Uniform patches of flow and substrate material within a geomorphic unit. Hydraulic Unit Individual elements (e.g., logs, rocks, gravel patches) within a stream. Microhabitat River Styles Hierarchy
GIS Data Atlas • TNC NFWF grant • GIS data atlas for the Caddo Lake watershed • West Gulf Coastal Plain aquatic conservation priorities • Considering development of data for River Styles Stage 1 analysis of Big Cypress Bayou watershed • TNC aquatic ecosystems classification • Many river characteristics calculated in a GIS • Consider data’s usefulness for River Styles • Consider developing additional data in the data atlas work
TNC Aquatic Ecosystems Classification • Mapped in 1:100K National Hydrography Dataset • Variables: • Watershed area • Gradient • Contributing area geology • Longitudinal connectivity
River Styles for Big Cypress Watershed? • Undertake a River Styles analysis for Big Cypress Bayou watershed? • Value added? • Relationship to other studies (e.g., channel cross-sections)? • Relationship to characterization, classification of hydrologic regime • What are the most important aspects of river characteristics in the area that would need to be included in the development of River Styles here? • Watershed characteristics? • Landscape, geomorphic unit characteristics? • What data are needed? • Is TNC’s data useful? What else needed? • Limitation of geomorphology expertise
Watershed River Styles: Australian Example Namoi River Basin, New South Wales Macdonald/Manilla Sub-basin Lower Namoi Sub-basin Peel Sub-basin Middle Namoi Sub-basin 50 0 25 75 100 Kilometers Mooki Sub-basin
Watershed Landscape Unit River Styles: Australian Example Namoi River Basin, New South Wales 50 0 25 100 Kilometers Legend – Landscape Units Liverpool plains Pillaga outwash Lowland plains Rugged metasediments Mid to lower Peel Rugged volcanics Pillaga Uplands
Landscape Unit River Style Uplands Escarpment Base of the Escarpment Rounded Foothills Lowland Plain Channel Slope Channel and Valley Width Planform Valley Cross Section Head-water Cut & Fill (Incised) Vertically Accreated Floodplain Floodplain Accumulation Floodout Cut & Fill (Intact) Fan Throughput Transfer Gorge
Watershed Landscape Unit River Style River Styles: Australian Example Middle Namoi Sub-basin 50 0 25 Kilometers
Geomorphic Unit Microhabitat Hydraulic Unit Trailing Vegetation Backwater Rippled flow on cobbles Submerged Macrophyte Riffle Barely perceptible flow on sand Cobbles Smooth surface flow on cobbles/sand Floodplain Large Woody Debris Pool Smooth surface flow on cobbles Bar Run Secondary Channel Boulders Sand Pool Leaf Pack Barely perceptible flow on sand/boulders