1 Byung Sik, Kim Kangwon National University Advanced Hydrology and Water Resources Management

Introduction to GIS

Presentation Outline Using GIS to connect hydrology and meteorology Representation of spatial objects in GIS Terrain analysis using Digital Elevation Models Geodesy and map projections

Hydrologic Cycle: Connecting the Land Surface with the Atmosphere

Connecting Hydrology and Meteorology Two Spatial Scales –Drainage basin scale for consideration of severe storms and flood (Nexrad radar precipation as input, flood runoff as output) –Regional or global scale for consideration of climate change (Global climate models as input, time series of river flows as output)

Regional flood analysis in Houston Study region

Nexrad Rainfall for Storm of Oct 1994

Discharge in Buffalo Bayou at Katy October, 1994 storm

Calibrated Flow with HEC-HMS

Global Runoff (mm/yr) According to NCAR’s CCM3.2 Global Climate Model (GCM)

GTOPO ” Digital Elevation Model of the Earth Source:

Drainage in North America Source:

Drainage Basins of North America Source: na_basins.html

Streamflow Hydrographs for Large Basins Amazon River Yangtze River Congo River MacKenzie River Runoff Input from Climate Model Streamflow Output at River Mouth

A Fundamental Dilemma Land Surface Hydrology has: –drainage patterns organized by rivers and watersheds which are spatially discrete –analysis in Cartesian coordinates (x,y,z) Atmospheric Science has: –circulation patterns which are spatially continuous over the earth –analysis in Geographic coordinates ( ,, z) GIS can be used to connect these two spatial frameworks

Presentation Outline Using GIS to connect hydrology and meteorology Representation of spatial objects in GIS Terrain analysis using Digital Elevation Models Geodesy and map projections

Discrete and Continuous Space Discrete Space: Vector GIS Continuous Space: Raster GIS

Geospatial Database: a set of compatible data layers or themes

Spatial Data: Vector format Point Point - a pair of x and y coordinates (x 1,y 1 ) Line Line - a sequence of points Polygon Polygon - a closed set of lines Node vertex Vector data are defined spatially:

Feature Attribute Table Fields Records

Relational Linkages Spatial Attributes Descriptive Attributes Water Right Locations

Locations on the Stream Network Digital Stream Network Connects Control Point Locations

Watersheds defined using a Digital Elevation Model

Spatial Data: Raster format Number of rows Number of Columns (X,Y) Cell size NODATA cell Definition of a Grid in GIS

Points as Cells

Line as a Sequence of Cells

Polygon as a Zone of Cells

Raster-Vector Data Model Raster Vector Real World

Presentation Outline Using GIS to connect hydrology and meteorology Representation of spatial objects in GIS Terrain analysis using Digital Elevation Models Geodesy and map projections

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

DEM Elevations Contours

Eight Direction Pour Point Model

Slope: Direction of Steepest Descent

Flow Direction Grid

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 LinkLink to Grid calculator

Flow Accumulation > 5 Cell Threshold

Stream Network for 5 cell Threshold Drainage Area

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

Watershed Outlet

Watershed Draining to This Outlet

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

DEM Data Sources 30m DEMs from 1:24,000 scale maps (urban watersheds) 3" (100m) DEMs from 1:250,000 scale maps (rural watersheds) 15" (500m) DEM for the US resampled from 3” DEM (large drainage basins) 30" (1km) DEM of the earth (GTOPO30)

Presentation Outline Using GIS to connect hydrology and meteorology Representation of spatial objects in GIS Terrain analysis using Digital Elevation Models Geodesy and map projections

Coordinate System (  o, o ) (x o,y o ) X Y Origin A planar coordinate system is defined by a pair of orthogonal (x,y) axes drawn through an origin

Earth to Globe to Map Representative Fraction Globe distance Earth distance = Map Scale: Map Projection: Scale Factor Map distance Globe distance = (e.g. 1:24,000) (e.g )

Map-Based Flood Hydrology and Hydraulics

Map-Based Hydrology and Hydraulics Connecting ArcView with HMS for the Austin Region Flood simulation using Nexrad data in Houston HMS-RAS for Waller Creek in Austin Creating flood plain maps in Waller Creek

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

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

DEM Watersheds for Austin

Selected Watersheds and Streams Mansfield Dam Colorado River

HMS Schematic Prepared with CRWR-PrePro Mansfield Dam Colorado River

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

HMS Control File

HMS Results Watershed 155Junction 44

Map-Based Hydrology and Hydraulics Connecting ArcView with HMS for the Austin Region Flood simulation using Nexrad data in Houston HMS-RAS for Waller Creek in Austin Creating flood plain maps in Waller Creek

Regional flood analysis in Houston Study region

Study Region in West Houston Maps Developed using CRWR-Prepro by Seth Ahrens

Nexrad Rainfall for Storm of Oct 1994

Discharge in Buffalo Bayou at Katy October, 1994 storm

Calibrated Flow with HEC-HMS

Map-Based Hydrology and Hydraulics Connecting ArcView with HMS for the Austin Region Flood simulation using Nexrad data in Houston HMS-RAS for Waller Creek in Austin Creating flood plain maps in Waller Creek

Waller Creek DEM

Waller Creek Watershed Outlets

Waller Creek HMS Model

Flood Plain Mapping

Connecting HMS and RAS

Discharge at a Particular Cross-Section

Map-Based Hydrology and Hydraulics Connecting ArcView with HMS for the Austin Region Flood simulation using Nexrad data in Houston HMS-RAS for Waller Creek in Austin Creating flood plain maps in Waller Creek

HEC-RAS: Background Hydraulic 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

For more information about GIS and Hydrology, see To obtain CRWR-PrePro to link ArcView with HEC-HMS, see To take an online spatial hydrology course, see Web Links