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Overland and Channel Routing in the Distributed Model

Overland and Channel Routing in the Distributed Model. Lecture 4a. Yu Zhang. Outline. Conceptual model Parameter estimation Connectivity Slopes Channel hydraulic properties Local customization steps. Routing Model. Real HRAP Cell. Hillslope model. Cell-to-cell channel routing.

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Overland and Channel Routing in the Distributed Model

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  1. Overland and Channel Routing in the Distributed Model Lecture 4a Yu Zhang

  2. Outline • Conceptual model • Parameter estimation • Connectivity • Slopes • Channel hydraulic properties • Local customization steps

  3. Routing Model Real HRAP Cell Hillslope model Cell-to-cell channel routing

  4. Separate Treatment of Fast and Slow Runoff

  5. HRAP Cell-to-cell Connectivity Examples ABRFC ~33,000 cells • OHD delivers baseline HRAP resolution connectivity, channel slope, and hillslope slope grids for each CONUS RFC • HRAP cell-to-cell connectivity and slope grids are derived from higher resolution DEM data. MARFC ~14,000 cells

  6. Representative Slopes Are Extracted from Higher Resolution DEMS (North Fork of the American River (850 km2)) Slope (m/m) Main Channel Slope (1/2 HRAP Resolution) Average = 0.06 Channel slopes are assigned based on a representative channel with the closest drainage area. Slopes from 30-m DEM Hillslope Slope (1/2 HRAP Resolution) Average = 0.15 Slopes of all DEM cells within the HRAP pixel are averaged. Local Channel Slope (1/2 HRAP Resolution) Average = 0.11

  7. B A Main Channel Slope vs. Local Channel Slope Segment Slopes (m/m) • Slopes of each stream segment are calculated from the DEM (2) Model cell slopes are assigned from representative segments that most closely match either the cell’s cumulative or local drainage area. In this case, the slope of segment A is taken as the ‘main’ channel slope and slope of segment B is taken as the ‘local’ channel slope.

  8. Channel Routing Model • Uses implicit finite difference solution technique • Solution requires a unique, single-valued relationship between cross-sectional area (A) and flow (Q) in each grid cell (Q=q0Aqm) • Distributed values for the parameters q0 and qm in this relationship are derived by using • USGS flow measurement data at selected points • Connectivity/slope data • Geomorphologic relationships • Training on techniques to derive spatially distributed parameter grids is provided in this workshop

  9. Kinematic Wave Equations Solved by HL-RDHM: Hillslope Flow Koren et al. (2004) (continuity) (momentum) q = discharge per unit area of hillslope h = average overland flow depth Rs = fast runoff from water balance Sh = hillslope slope nh = hillslope roughness D = drainage density Lh = hillslope length Conceptual Hillslopes (higher D = more hillslopes and faster response)

  10. Kinematic Wave Equations Solved by HL-RDHM: Channel Flow Koren et al. (2004) ‘Kinematic’ wave solution assumes slope dominates all other forces (e.g. inertial (rapid changes), pressure, wind, tides) (continuity) (momentum) Q = channel discharge A = channel cross-sectional area qLh = overland flow rate at the hillslope outlet Rg = slow runoff component from the water balance Fc = grid cell area Lc = channel length within a cell

  11. Kinematic Wave vs. Unit Hydrograph Larger flood accelerated Same q0,qm Treating KW 25.4 like UG Smaller flood delayed • If (qm != 1), channel velocity will vary with flow level (linear superposition does not apply). • Typically qm > 1, resulting in faster flood propagation at high flows. • If qm == 1, channel flow behavior would be similar to a unit hydrograph in the case of uniform runoff (overland flow velocity can still be flow dependent).

  12. Two Simple Channel-Flood Plain Models are Available in HL-RDHM • The ‘Rating Curve’ model estimates the parameters q0 and qm directly for each model cell using hydraulic measurements at an outlet gauging station, cell drainage areas, and geomorphologic relationships. • The ‘Channel shape’ method assumes a simple parabolic channel geometry and uses outlet hydraulic measurements, cell drainage areas, slopes, the Chezy-Manning equation, and geomorphologic relationships to estimate q0 and qm for each cell. • Both models have produced good results in our applications. q0 qm

  13. ‘Channel Shape’ Model • Assume simple relationship between top width (B) and depth (H) • Solve for a and b at a USGS gauge using streamflow measurement data • Use geomorphologic relationships to derive spatially variable a values (see Koren, 2004 for details) • Compute q0 and qm as a function of a and b, channel slope (Sc) and channel roughness (nc) b = 1 b < 1 b > 1 b = 0

  14. ‘Rating Curve’ Model • Solve for q0 and qm at a USGS gauge using streamflow measurement data • Use geomorphologic relationships to derive spatially variable a values (see Koren, 2004 for details)

  15. KNSO2 (285 km2) WATTS (1645 km2) Model Validation CAVESP (90 km2) SPRINGT (37 km2) Model predicted relationships (p) at points upstream from TALO2 (2484 km2) compared with local fits (l)

  16. Routing Parameter Grids • Default grid values: • rutpix_ALPHC: -1 (nodata) • rutpix_BETAC: 1 • rutpix_DS: 2.5 • rutpix_Q0CHN: -1 (nodata) • rutpix_QMCHN: 1.333 • rutpix_ROUGC: -1 (nodata) • rutpix_ROUGH: 0.15 Rutpix7 = ‘channel shape’ Rutpix9 = ‘rating curve’

  17. Routing Parameter Customization Procedures(User Manual Chapter 9) • Determine best HRAP cell to represent basin outlet (XDMS) • Add outlet to connectivity file header • Adjust cell areas so the total drainage area matches USGS area (cellarea program) • Download measurement data from USGS NWIS site • (optional) Use preprocess.R to parse USGS flow measurement data for multiple stations into separate files • Use outletmeas_manual.R to analyze station data • Use genpar utility program to generate grids

  18. 2258 km2 285 km2 795 km2 Model Resolution and Basin Size Considerations HRAP Cell Connectivity • Percent errors in representing basins with 4 km resolution pixels. • Open squares represent errors due to resolution only. • Black diamonds represent errors due to resolution and connectivity. • We correct for these errors by adjusting cell areas in the model so that the sum of the model cell areas matches the USGS reported area at the basin outlet.

  19. HRAP vs. ½ HRAP Implementation Area (km2) ID Gauge Name 2 1 3 4 km resolution does not allow accurate selection of an outlet for this subbasin because 2 km resolution allows more accurate delineation User must choose which cell is the best outlet for this basin.

  20. Connectivity File Example Change this number when adding outlets User defined header lines

  21. Outletmeas_manual.R: Additional Plots Q vs. A for Two Methods

  22. R Scripts Provided to Assist with Flow Measurement Analysis • Outletmeas_manual.R automatically generates several plots and computes reqressions • User can specify plotting and regression weight options • Derived parameters are saved to a file for later use

  23. Outletmeas_manual.R User Options #---(1)--- input file name file.list<-"/fs/hsmb5/hydro/users/sreed/flow_measurements/dmip2/talo2meas3_29_07.d" #---(2)--- user specified weight exponent for regression Qwt.qa<-1 # for Q-A Qwt.ab<-1 # for A-B Qwt.n <-1 # for Manning's n #---(3)--- User specified relative weights for each of the USGS data quality flags ws<-c(1,1,1,1,1) #--------------------------------- # Code Description # --------------------------------- # E Excellent the data is within 2% (percent) of the actual flow # G Good the data is within 5% (percent) of the actual flow # F Fair the data is within 8% (percent) of the actual flow # P Poor the data are not within 8% (percent) of the actual flow # -1 Missing # The ws vector is ordered as above c(E,G,F,P,-1) #---(4)--- graph options plot_quality=T new_graphics=T #---(5)--- info for the channel shape method slope=0.002 #reread_data=TRUE #--- (6)--- output file names file.out<-"param.final.d"

  24. Genpar Input Deck #genpar.card #enter the connectivity file name connectivity = /fs/hsmb5/hydro/users/zhangy/RDHM/Genpar/sequence/abrfc_var_adj.con #specify an input location for parameter grids input-path = /fs/hsmb5/hydro/rms/parameterslx/abrfc #specificy an output location output-path = /fs/hsmb5/hydro/users/zhangy/RDHM/Genpar/output #replace/update the existing grid or output the grid to the output-path, true or false # overwrite-existing-grid = false # #create a new grid instead of modify existing grid, the boundary in this # case is the boundary of all selected basins, true or false create-new-grid = true # #if the create-new-grid is true, the grid will be created in this window. #if this window is not consistent with the window from the connectivity, #the windows are combined into a big window that contains both subwindows. #window-in-hrap = 480 505 298 306 # # Name of the parameter to be created, available names are: # slopc rougc betac alphc sloph ds rough Q0CHN QMCHM # They are case insensitive #genpar-id = slopc #genpar-id = rougc #genpar-id = alphc #the next line specifies the parameter for which values will be generated genpar-id = q0chn #genpar-id = qmchn #next line is an example input information for q0chn grid generation genpar-data = TALO2 0.31 1.2 Table 9.3 tells you what to put here

  25. Required Arguments for Grid Generation Condensed Table 9.3

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