St. Johns River Water Management District. Tim Cera, P.E.

Transcription

1 Tim Cera, P.E.

2 North Florida/Southeast Georgia HSPF Models Needed watershed delineation for what ended up being 71 Hydrological Simulation Program FORTRAN (HSPF) Establish recharge and maximum saturated ET estimates for input into groundwater model Needed ability to delineate against many USGS flow gauges 2

3 What is TauDEM? Terrain Analysis Using Digital Elevation Models (TauDEM) Developed by Professor David Tarboton at Utah State University Actively maintained Used in other software Better Assessment Science Integrating Point and Non-point Sources (BASINS) Code freely available GPLv3 license 3

4 Why TauDEM? Command line versions available on Linux Useful on District s Linux cluster, now at almost 500 CPUs ArcGIS Toolbox QGIS extension Comprehensive set of programs Can work with large scale DEMs split across multiple rasters 4

5 Basic Grid Analysis Functions Command pitremove d8flowdir dinfflowdir aread8 dreadinf gridnet Description Identifies all pits in the DEM and raises their elevation to the level of the lowest pour point around their edge. Takes as input the hydrologically correct elevation grid and outputs D8 flow direction and slope for each grid cell. Assigns a flow direction based on steepest slope on a triangular facet following the D infinity model. Takes as input a D8 flow directions grid and outputs the contributing area as the number of grid cells draining through each grid cell. Takes as input a D infinity flow direction grid and outputs the specific catchment area. Specific catchment area is defined as contributing area per unit contour length. GridNet Takes as input a D8 flow directions file and outputs three grid files: - plen contains the path length from the furthest cell that drains to each cell. - tlen contains the total length of all paths draining to each cell. - gord contains the Strahler order associated with that cell for a flow network defined using the D8 flow directions and including each gridcell. 5

6 Command peukerdouglas threshold d8flowpathextremeup slopearea lengtharea dropanalysis streamnet Stream Network Development Functions Description Takes as input an elevation grid and outputs an indicator (1,0) grid of candidate stream cells according to the Peuker and Douglas algorithm. Takes as any grid and outputs an indicator (1,0) grid of grid cells that have values >= the input threshold. Evaluates the extreme (either maximum or minimum) upslope value from an input grid based on the D8 flow directions. Evaluates Sman based on slope and specific catchment area grid inputs, and parameters m and n. Uses with slope-area stream delineation. Evaluates A >= M Ly and outputs an indicator (1,0) grid based on upslope path length and D8 contributing area grid inputs, and parameters M and y. Applies a series of thresholds and outputs a table of stream statistics used in objectively selecting the stream delineation threshold. Produces a vector network (shapefile) from a stream raster grid. Outputs a grid of subwatersheds draining to each stream network link. 6

7 Stream Network/Outlet Functions Command moveoutletstostreams gagewatershed Description Adjusts the position of outlets by moving them downslope along D8 flow directions until they reach a stream. Calculates Gage watersheds grid. Each grid cell is labeled with the identifier (from column id) of the gage to which it drains directly without passing through any other gages. 7

8 Specialized Grid Analysis Functions Command slopearearatio d8hdisttostrm dinfupdependence dinfdecayaccum dinfconclimaccum dinftranslimaccum dinfrevaccum dinfdistdown/ dinfdistup dinfavalanche slopeavedown twi Description Calculates ratio S/A where S is slope and A contributing area Calculates horizontal distance to stream along D8 flow directions Calculates upslope dependence Calculates decay limited accumulation Calculates concentration limited accumulation Calculates transport limited accumulation Calculates reverse accumulation Calculates distance downslope/upslope to a target zone (typically stream) using Dinf flow directions. Calculates avalanche runout zone and distance to avalanche source in avalanche runout zone Calculates slope averaged over specified distance down D8 flow directions Calculates Topographic Wetness Index (TWI). This provides an indication of depth to water table. No data values occur in locations where slope is 0 (flat). 8

9 Hydro-enforced DEM Known locations of water features like streams and watershed boundaries are burned into the DEM by altering the elevation values National Hydrography Dataset Plus (NHD+) has a hydro-enforced DEM based on the National Elevation Dataset (NED) 10,000 feet is subtracted from the cells that lie along know streams 10,000 feet is added to cells that lie along HUC8 and HUC12 boundaries 9

10 Reservoirs (Flat Areas) 10

11 Final 11

12 Final vs NHDPlus v2 12

13 Final vs NHDPlus v2 13

14 TauDEM Problems pitremove Necessary step to fix small pits or errors in the DEM that would cause problems for other programs to work correctly A closed basin is seen as a pit to fill Once filled by pitremove, closed basins are represented by very large flat areas Flat areas; lakes, wetlands, The process of establishing a stream network is very difficult without some elevation relief Frontal basins facing the ocean or large lakes Basins with multiple outlets 14

15 TauDEM Solutions Split watershed into separate areas Tributary basins Closed basins Flat basins (swamps and marshes) Frontal basins (multiple outlets) 15

16 Closed Basins 16

17 NFSEG Workflow Apply TauDEM processing workflow to each group using different parameters for each pitremove d8flowdir aread8 threshold streamnet/moveoutlettostream 17

18 Final Delineation 18