1. 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, 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

2. 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?

3. 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.

4. 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.

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

6. 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

7. 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

8. Terrain Analysis Burning-in streams DEM creek Digitized creek45 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

9. Terrain Analysis
DEM and digitized reach network

10. 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.

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

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

13. 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.

14. 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.

15. 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.

16. 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.

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

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

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

20. 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.

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

22. 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.

23. 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.

24. 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)

25. 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)

26. 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).

27. 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)

28. 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

29. 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.

30. Hydrologic Sub-System
Manual selection of sub-basin polygons

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

32. Topologic Analysis
HEC-HMS schematic in ArcView.

33. Topologic Analysis
HEC-HMS schematic in HMS.

34. Topologic Analysis

35. 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

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

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

38. User-Specified Gage Weighting
Precipitation model in HEC-HMS

39. GridParm
Precipitation cells for modClark sub-basin routing.

40. GridParm
Precipitation cells for modClark sub-basin routing.

41. 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.

42. Basin File Watershed Parameters

43. Basin File Watershed Parameters

44. Basin File Stream Parameters

45. Precipitation File

46. Control File

47. Hydrograph Time Table

48. Hydrograph Summary

49. Hydrograph Plot