Post on 19-Jan-2018
description
CRWR-PreProStream and Watershed Delineation
Francisco Olivera, Ph.D.Center for Research in Water Resources
University of Texas at Austin
Texas Department of Transportation (TxDOT)Water Resources Modeling Using GIS2000 - Austin, Texas
What is CRWR-PrePro?
Digital Spatial Data
Data for HEC-HMS Input Components
(Not all HMS options are included yet)
CRWR-PrePro
CRWR-PrePro is an ArcView pre-processor of digital spatial data for the HEC’s Hydrologic Modeling System (HMS)
What is HEC-HMS?
HEC-HMS “is a new generation software for precipitation-runoff simulation that supersedes the HEC-1 Flood Hydrograph Package.” (HEC-HMS User’s Manual)
HEC-HMS is a Windows version of HEC-1.
What is HEC-HMS?
ControlDefinition of the
analysis time window.
Precipitation
Definition of rainfall data in
time and space.
BasinDefinition of the
hydrologic elements.
HEC-HMSSimulation
Hydrographs
Stream-Watershed Delineation
Terrain Analysis
Stream-Watershed Delineation
Terrain Analysis
Burn-In Streams[Grid]
Fill Sinks[Grid]
Flow Direction[Grid]
Flow Accumulation[Grid]
DEM[Grid]
DigitizedStream Network
[Line Coverage]
Terrain Analysis71
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 128Hydrologic functions
Terrain Analysis
DEM and digitized reach network
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
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.
Stream-Watershed Delineation
Stream NetworkDefinition
Watershed Delineation
Watershed OutletDefinition
Raster to VectorConversion
Stream Network Definition
AutomaticCells draining more area
than a user-defined threshold value.
InteractiveCells located downstream of
user-identified cells.
Stream Network[Grid]
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.
Watershed Outlet Definition
AutomaticMost downstream cells of
the stream segments
InteractiveUser-identified cells
[outlets, reservoirs, control points, etc.]
Watershed Outlets[Grid]
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.
Watershed Delineation
Watershed Delineation
Watershed Outlets
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.
Merging Polygons and Watersheds
WatershedVectorization
StreamVectorization
MergingWatersheds
Dissolving SpuriousPolygons
Merging Spurious Polygons
Cells connected to the main watershed polygon through a corner are defined as a separate polygon (spurious polygon).
These polygons are dissolved into the main polygon.
Merging Watersheds Adjacent watershed polygons can be merged into a single
polygon, if they share the outlet or one flows into the other.
Merging Watersheds
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.