Introduction to GIS in Water Resources

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Introduction to GIS in Water Resources

• Ceve 512
• January 12, 2006

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Geographic Information SystemsA Definition of GIS

• GIS is a system composed of three integral parts
• A Database
• Spatial or Map Information
• Some way to link the two
• Computer
• GIS Software
• Trained Users
• Spatial location usually a geographic location
• Information visualization of analysis of data
• System linking software, hardware, data
• Trained User a thinking explorer who is key to
  the power of GIS

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What is Not GIS?

• GPS Global Positioning System
• A Static Map Paper or Digital
• Maps are often a product of GIS
• A way to visualize the analysis
• A Software Package

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What is GIS?

• A method to visualize, manipulate, analyze, and
  display spatial data.
• Smart Maps that link a database to
  corresponding map locations.
• Zoom in while still preserving information.

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Database Composition

• Feature
• An Item or piece of information placed on a map.
• Point (1 location), line, area
• Activities
• Described with geographical pattern and
  distribution.
• Population maps, urban infrastructure maps
• Events
• Occurs at a point in time and can be mapped over
  time.
• Rainfall events

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Combining Data from Many Sources

• Digitized and Scanned Maps
• Purchased, Internet
• Created by user
• Data Bases Tables of Data
• GPS Global Positioning System
• Accurate locations
• Field Sampling of Attributes
• Remote Sensing and Aerial Photography

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Data Model Based on Inventory
GIS Layers combine as Geospatial Database

• Streams
• Drainage Areas
• Hydrography
• Channels
• Terrain Surfaces
• Rainfall Response
• Digital Orthophotos

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Turning Data into Information

• Five Data Layers Features Match
• Georeferenced Overlays

Spatial Analysis Not Just A Map
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Two Ways to Input and Visualize DataThe World in
GIS

• Raster Grid
• pixels
• A location and value
• Satellite images and aerial photos are already in
  this format
• Vector Linear
• Points, lines and polygons
• Features (house, lake, etc.)
• Attributes
• Size, length, type, etc.

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Spatial Data Vector Format
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Vector Data

• Create or Download Themes
• Polygons Outline of Texas Counties
• Lines Texas Rivers
• Points Texas Cities

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Example Subwatersheds in Houston

• Flooded HISD schools during Tropical Storm
  Allison.

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Raster Data

• Raster Data are described by a cell grid, one
  value per cell. (Elevation for Example)
• Downloaded from the USGS and other government
  agencies.

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Example Rainfall (annual or event)

• Overlay previous map with rainfall values to
  determine flooded areas.

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Example Digital Elevation Model (DEM)
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Comparison of Raster and Vector Data
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Combining Raster and Vector Data
Integrated Raster-Vector Database
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Aerial PhotographsDigital Orthophoto Quadrangles
(DOQs)

• USGS maps

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Location MapsDigital Raster Graphics (DRGs)

• Topographic maps

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Applying GIS

• Some Ways GIS is Used
• Emergency Services Fire, Police, Rescue
• Environmental Monitoring and Modeling
• Business Site Location, Delivery Systems
• Industry Transportation, Communication, Mining,
  Pipelines, Healthcare
• Education Research, Teaching Tool,
  Administration
• Wherever Spatial Data Analysis is Needed

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Asking a Question Interaction
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Multiple Databases can be Linked and Related
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3D Groundwater Well Data
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Environmental Modeling Contamination Plumes
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Combining Various Display Methods
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Modeling of Future Trends
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Geo-HMS Terrain Processing

• Apply DEM to automatically create Flow Direction
  Grid
• Create Flow Accumulation Grid
• Choose threshold value to generate streams
• Delineate Watershed
• Sub watersheds obtained from this process

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Flow Accumulation

• Direction of Steepest Descent
• Flow Direction Grid

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Step 1 Terrain Processing
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Step 2 Terrain Processing
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Step 3 Terrain Processing
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Sample Project Outline

• Acquire DOQs, DEMs, and DRGs
• Define watersheds and rivers using Geo-HMS
  terrain processing
• Create Hydrologic (HMS) model from Geo-HMS
• Input known rainfall data
• Solve flooding issues

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Sample GIS Floodplains