CRWR-PrePro: A System ofGIS Tools for HEC-HMS Modeling Support

Francisco “Paco” Olivera, Ph.D.Center for Research in Water Resources

University of Texas at Austin

19th ESRI International User ConferenceWater ResourcesRainfall Runoff Modeling Using GIS and HEC-HMSJuly 25, 1999 - San Diego, California

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

ControlDefinition of the analysis

time window.

PrecipitationDefinition of rainfall data

in time and space.

BasinDefinition of the

hydrologic elements of the system.

HEC-HMSSimulation

What is CRWR-PrePro?

Digital Spatial Data

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

71

56

445369

74

78 72 69

4768

58 55

21

31

67

58

49 46

37 38

64 22

61 16

Digital elevation model (DEM)

22

2 2 2

2

4 4

4 4

1 1 2 4 8

128

128 1 2 4

128 1 41

128

Flow direction grid Flow accumulation grid

0 0 0 0 0

0 1 1 2 1

0

0

0 0 0

3 8 5 2

1 1 20 0

1 24

Stream Network

Flow direction codes

1

248

16

32 64 128

Hydrologic functions

Terrain Analysis

45

44

38

34

40

45

50

60

58

31

30

53

50

45

32

22

DEM creek

45

44

38

34

40

45

50

60

58

31

30

53

50

45

32

22

Digitized creek

38

34

30

22

Digitized creek

145

144

138

134

140

145

150

160

158

131

130

153

150

145

132

122

Raised DEM

145

144

38

34

140

145

150

160

158

131

30

153

150

145

132

22

Burned-in DEM

Burning-in streams

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

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

t5.3,

S67.31

]9)CN/1000[(Lmaxt

5.0

7.08.0w

p

tp: sub-basin lag-time (min)LW: length of sub-basin longest flow-path (ft)CN: average Curve Number in sub-basinS: slope of the sub-basin longest flow-path (%)t: analysis time step (min)

Sub-basin lag-time according to the SCS formula:

Hydrologic Parameters

t5.3,

V60

L3048.06.0maxt

w

wp

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)

Sub-basin lag-time according to 0.6 L/v formula:

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

s

slag V60

Lt

tlag: reach lag-time (min)Ls: length of reach (m)Vs: reach average velocity (m/s)

Reach lag-time for Pure Lag routing:

Hydrologic Parameters

s

s

V3600

LK

K: Muskingum parameter K (hr)X: Muskingum parameter XLs: reach length (m)Vs: reach average velocity (m/s)n: number of sub-reaches

1t

V60/LX2intn ss

Reach lag-time and number of sub-reaches for Muskingum routing:

Hydrologic Parameters

Pure lag routing for Ls/60vs < t, 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 FileWatershed Parameters

Basin FileWatershed Parameters

Basin FileStream Parameters

Precipitation File

Control File

Hydrograph Time Table

Hydrograph Summary

Hydrograph Plot