CRWR-PrePro: A System of GIS Tools for HEC-HMS Modeling Support 19th ESRI International User Conference Water Resources Rainfall Runoff Modeling Using GIS and HEC-HMS July 25, 1999 - San Diego, California CRWR-PrePro: A System of GIS Tools for HEC-HMS Modeling Support Francisco “Paco” Olivera, Ph.D. Center for Research in Water Resources University of Texas at Austin

The Team David Maidment, Ph.D. Seann Reed, Ph.D. Ximing Cai, Ph.D. Ferdinand Hellweger Aubrey Dugger Francisco Olivera, Ph.D. How many Ph.D.’s do you need to develop CRWR-PrePro?

What is HEC-HMS? “It is a new generation software for precipitation-runoff simulation that supersedes the HEC-1 Flood Hydrograph Package.” (HEC-HMS User’s Manual) It is a Windows version of HEC-1.

HEC-HMS Input Components Control Definition of the analysis time window. Basin Definition of the hydrologic elements of the system. HEC-HMS Simulation Precipitation Definition of rainfall data in time and space.

What is CRWR-PrePro? Digital Spatial Data CRWR-PrePro Data for HEC-HMS Input Components (Not all HMS options are included yet) CRWR-PrePro

Overview Input Data for the HEC-HMS Basin Component Raster-Based Terrain Analysis Raster-Based Sub-Basin and Reach Network Delineation Vectorization of Sub-Basins and Reach Segments Computation of Hydrologic Parameters of Sub-Basins and Reaches Extraction of Hydrologic Sub-System Topologic Analysis Input Data for the HEC-HMS Precipitation Component User-Specified Gage Weighting GridParm

Terrain Analysis Hydrologic functions 78 72 69 71 58 Flow direction codes 1 2 4 8 16 32 64 128 Hydrologic functions 74 67 56 49 46 69 53 44 37 38 64 58 55 22 31 68 61 47 21 16 Digital elevation model (DEM) 2 4 1 8 128 Flow direction grid 1 1 2 1 3 8 5 2 1 1 20 1 24 Flow accumulation grid Stream Network

Terrain Analysis Burning-in streams DEM creek Digitized creek 45 44 38 34 40 50 60 58 31 30 53 32 22 DEM creek 45 44 38 34 40 50 60 58 31 30 53 32 22 Digitized creek Burning-in streams 38 34 30 22 Digitized creek 145 144 138 134 140 150 160 158 131 130 153 132 122 Raised DEM 145 144 38 34 140 150 160 158 131 30 153 132 22 Burned-in DEM

Terrain Analysis DEM and digitized reach network

Terrain Analysis Burned-in DEM Elevation is increased by a fixed value in all cells, except for those that coincide with the digitized reach network.

Terrain Analysis Flow direction Water flows to one of the eight neighbor cells, according to the direction of the steepest descent.

Terrain Analysis Flow accumulation Measure of the drainage area in units of grid cells.

Sub-Basins and Reach Network Grid cells draining more than a user-defined threshold value (blue streams), or located downstream of user-defined cells (red streams) are part of the reach network.

Sub-Basins and Reach Network Reach segmentation. Reach segments (links) are the sections of a reach channel connecting two successive junctions, a junction and an outlet, or a headwater and a junction.

Sub-Basins and Reach Network Watershed outlets. The most downstream cells of the reach segments (brown cells), and user-defined cells (red dots) are potential sub-basin outlets.

Sub-Basins and Reach Network Modified reach segmentation. The user-defined outlets modify the reach segmentation by splitting the segments in which they are located.

Sub-Basins and Reach Network Sub-basin delineation. The drainage area of each sub-basin outlet is delineated.

Vectorization Streams and watersheds are converted from raster to vector format.

Vectorization Adjacent watershed polygons can be merged into a single polygon, if they share the outlet or one flows into the other.

Vectorization After merging sub-basin polygons, the attribute tables are modified so that the watershed code (WshCode) of the reaches and the area of the new sub-basin are updated.

Hydrologic Parameters Flow length downstream to the sub-basin outlet.

Hydrologic Parameters Flow length upstream to the sub-basin divide. A NODATA cell is defined at the sub-basin outlets before running the flow length function.

Hydrologic Parameters Sub-basin longest flow-path. The longest flow-path is the geometric locus of the points for which the sum of both flow lengths is a maximum.

Hydrologic Parameters Sub-basin lag-time according to the SCS formula: tp: sub-basin lag-time (min) LW: length of sub-basin longest flow-path (ft) CN: average Curve Number in sub-basin S: slope of the sub-basin longest flow-path (%) t: analysis time step (min)

Hydrologic Parameters Sub-basin lag-time according to 0.6 L/v formula: tp: sub-basin lag-time (min) Lw: length of sub-basin longest flow-path (ft) Vw: average velocity sub-basin longest flow-path (m/s) t: analysis time step (min)

Hydrologic Parameters Sub-basin parameters: Grid code, area (Km2), unit hydrograph model (SCS), length of longest flow path (m), slope of longest flow path (fraction), average curve number, lag-time (min), baseflow (none).

Hydrologic Parameters Reach lag-time for Pure Lag routing: tlag: reach lag-time (min) Ls: length of reach (m) Vs: reach average velocity (m/s)

Hydrologic Parameters Reach lag-time and number of sub-reaches for Muskingum routing: K: Muskingum parameter K (hr) X: Muskingum parameter X Ls: reach length (m) Vs: reach average velocity (m/s) n: number of sub-reaches

Hydrologic Parameters Pure lag routing for Ls/60vs < Dt, otherwise Muskingum routing. Reach parameters: Grid code, sub-basin code, length(m), velocity (m/s), routing method (Lag or Muskingum), lag time (min), Muskingum X, Muskingum K (hr), number of sub-reaches.

Hydrologic Sub-System Manual selection of sub-basin polygons

Hydrologic Sub-System Manual selection of most downstream sub-basin polygon.

Topologic Analysis HEC-HMS schematic in ArcView.

Topologic Analysis HEC-HMS schematic in HMS.

Topologic Analysis

Overview Input Data for the HEC-HMS Basin Component Raster-Based Terrain Analysis Raster-Based Sub-Basin and Reach Network Delineation Vectorization of Sub-Basins and Reach Segments Computation of Hydrologic Parameters of Sub-Basins and Reaches Extraction of Hydrologic Sub-System Topologic Analysis Input Data for the HEC-HMS Precipitation Component User-Specified Gage Weighting GridParm

User-Specified Gage Weighting Intersection of sub-basin polygons with gage Thiessen polygons.

User-Specified Gage Weighting Precipitation in each sub-basin is calculated as a weighted average of the precipitation in the gages.

User-Specified Gage Weighting Precipitation model in HEC-HMS

GridParm Precipitation cells for modClark sub-basin routing.

GridParm Precipitation cells for modClark sub-basin routing.

Conclusions CRWR-PrePro pre-processes digital spatial data and produces input data for the HEC-HMS basin and precipitation components. CRWR-PrePro supports six of the seven hydrologic elements used in HEC-HMS. Within these elements it supports the SCS unit hydrograph for sub-basin routing, pure lag and Muskingum for reach routing, curve number and initial-plus-constant for precipitation excess calculations. CRWR-PrePro supports the user-specified-gage-weighting and GridParm for spatial interpolation of precipitation data.

Basin File Watershed Parameters

Basin File Watershed Parameters

Basin File Stream Parameters

Precipitation File

Control File

Hydrograph Time Table

Hydrograph Summary

Hydrograph Plot