Hydrologic Cycle

Hydrologic Cycle Processes Surface Water Soil water Atmospheric water Groundwater Processes Precipitation Evaporation Surface Runoff Groundwater Recharge Baseflow

Map-Based Hydrology and Hydraulics ArcView Input Data DEM HEC-HMS Flood discharge HEC-RAS Water surface profiles ArcView Flood plain maps CRWR-PreProAvRAS

GIS-Based Flood Modeling Terrain analysis using Digital Elevation Models Flood hydrology model for the Austin region Creating flood plain maps for Waller Creek Real time flood emergency management

Study Region in West Austin Hog Pen Ck 4 km

Watershed Delineation by Hand Digitizing Watershed divide Drainage direction Outlet

30 Meter Mesh Standard for 1:24,000 Scale Maps

DEM Elevations Contours

Eight Direction Pour Point Model

DEM Elevations Contours

Austin West 30 Meter DEM Elevations in meters ftp://ftp.tnris.state.tx.us/tnris/demA.html

Flow Direction Grid

Grid Network

Flow Accumulation Grid

Flow Accumulation > 5 Cell Threshold

Streams with 200 cell Threshold (>18 hectares or 13.5 acres drainage area)

Watershed Draining to This Outlet

Watershed and Drainage Paths Delineated from 30m DEM Automated method is more consistent than hand delineation

DEM Data Sources Digital terrain models with 2’ or 4’ contours built from aerial photogrammetry 10m DE-DEMs, from 1:24,000 scale maps with drainage enforcement (experimental) 30m DEMs from 1:24,000 scale maps 1 " seamless DEM of Texas (March, 1999) 3" (100m) DEMs from 1:250,000 scale maps (current state-wide coverage) 30” (1km) DEMs global coverage

7.5´ 1º 3" (100m) DEM 30m DEM Coverage of DEMs 1” seamless DEM

Cell Size30m (1”)100m (3”)

GIS-Based Flood Modeling Terrain analysis using Digital Elevation Models Flood hydrology model for the Austin region Creating flood plain maps for Waller Creek Real time flood emergency management

Map-Based Hydrology and Hydraulics ArcView Input Data DEM HEC-HMS Flood discharge HEC-RAS Water surface profiles ArcView Flood plain maps CRWR-PreProAvRAS

Austin Digital Elevation Model Waller Creek

Austin Watersheds

CRWR-PrePro ArcView-based preprocessor for HEC-Hydrologic Modeling System (HEC-HMS) Digital Elevation Model Stream Map HMS Basin File Control point locations Soil and Land Use Maps

DEM Watersheds for Austin

Selected Watersheds and Streams Mansfield Dam Colorado River

HMS Schematic Prepared with CRWR-PrePro Mansfield Dam Colorado River

SCS Runoff Curve Number method determines the direct runoff from storm rainfall in small watersheds. Curve number (CN) is a function of hydrologic soil group and land use.

HMS Basin File Basin file is a text description of all hydrologic elements Subbasin Junction Reach

HMS Model of the Austin Region

Design Precipitation Input

Maps Served on the Web

Nexrad Rainfall for Storm of Oct 1994

HMS Results Watershed 155Junction 44

GIS-Based Flood Modeling Terrain analysis using Digital Elevation Models Flood hydrology model for the Austin region Creating flood plain maps for Waller Creek Real time flood emergency management

Map-Based Hydrology and Hydraulics ArcView Input Data DEM HEC-HMS Flood discharge HEC-RAS Water surface profiles ArcView Flood plain maps CRWR-PreProAvRAS

Waller Creek DEM

Waller Creek HMS Model

Flood Plain Mapping

Connecting HMS and RAS

Discharge at a Particular Cross-Section

Map-Based Hydrology and Hydraulics ArcView Input Data DEM HEC-HMS Flood discharge HEC-RAS Water surface profiles ArcView Flood plain maps CRWR-PreProAvRAS

HEC-RAS: Background River Analysis System model of the U.S. Army Corps of Engineers Input = cross-section geometry and flow rates Output = flood water elevations Cross-Section Schematic

Points describe channel and floodway geometry Bank station locations Water surface elevations and floodplain boundaries HEC-RAS: Cross-Section Description

HEC-RAS: Output Text File Graphical

Data translation from HEC-RAS text file to dbase table Bank and floodplain boundaries measured from stream centerline HEC-RAS: Data Translation

Digital orthophotograph and road coverage used as a base map User digitizes stream with mouse Boundary points define the RAS stream Digital Stream Mapping

Floodplain Mapping: Plan View

3D Terrain Modeling: Ultimate Goal

GIS-Based Flood Modeling Terrain analysis using Digital Elevation Models Flood hydrology model for the Austin region Creating flood plain maps for Waller Creek Real time flood emergency management

Real-time flood emergency mapping Flood hydrology analysis system Nexrad radar rainfall input Precomputed flood map library Real time Offline