GIS Modeling

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GIS Modeling

• Venkatesh Merwade, University of Texas at Austin

Interdisciplinary aquatic modeling workshop, July
21, 2005
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Overview

• GIS and data representation
• Geodatabase design
• Vector and surface analysis
• 3D and visualization in GIS
• GIS and Modeling
• Case studies

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Geographic Data Model

• Conceptual Model a set of concepts that
  describe a subject and allow reasoning about it
• Mathematical Model a conceptual model expressed
  in symbols and equations
• Data Model a conceptual model expressed in a
  data structure (e.g. ascii files, Excel tables,
  ..)
• Geographic Data Model a conceptual model for
  describing and reasoning about the world
  expressed in a GIS database

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Data Model based on Inventory of data layers
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Vector Data
(x2, y2)
(x2, y2)
(x1, y1)
(x1, y1)
(x1, y1)
(x1, y1)
(x4, y4)
(x1, y1)
(x3, y3)
(x1, y1)
Point pair of (x,y) coordinates
Line a sequence of points
Polygon a closed set of lines
All vector shapes (2D and 3D) are made from a set
of points.
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Vector Data for Guadalupe Basin in Texas
Monitoring Points USGS gaging stations
Stream Network Low resolution NHD Flowlines
Watershed 8 digit HUC units
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Measure in ArcGIS
A PolylineMZ can store m and z at each vertex
along with x and y coordinates.
64.0056
112.3213
0
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Raster Data
Number of columns
Cell Size
Number of rows
Cell
Cell Value
Example, Digital Elevation Model
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Raster ?? Vector
Vector
Raster
Point
Line
Zone of cells
Polygon
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Triangulated Irregular Network
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How do we combine these data?
Digital Elevation Models
Streams
Watersheds
Waterbodies
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An integrated raster-vector database
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Overview

• GIS and data representation
• Geodatabase design
• Vector and surface analysis
• 3D and visualization in GIS
• GIS and Modeling
• Case studies

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Geodatabase Design
GeoDatabase (stores geographic data organized
into datasets and feature classes )
Feature Dataset (collection of feature classes
and relationship classes)
Raster Catalog (a collection of raster datasets)
Polyline Feature class
Point Feature class
Polygon Feature class
Relationship class
Object class
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Data Model Based on Behavior
Follow a drop of water from where it falls on
the land, to the stream, and all the way to the
ocean. R.M. Hirsch, USGS
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Integrating Data Inventory using a Behavioral
Model
Relationships between objects linked by tracing
path of water movement
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Arc Hydro Data Model

• A geospatial and temporal data model for water
  resources

Arc Hydro framework
HydroEdge
Watershed
Personal Geodatabase
HydroJunction
Feature Dataset
Network
Hydro Edge
Hydro Junction
Watershed
Relationships
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Overview

• GIS and data representation
• Geodatabase design
• Vector and surface analysis
• 3D and visualization in GIS
• GIS and Modeling
• Case studies

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Vector Analysis

• Attribute tools
• Join/relate, calculations
• Topology and Network analysis
• geometric networks and solvers
• Geo-processing
• Batch processing of geometries

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Attribute Relationships
ReachHasCrossSections
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Calculations using vector attributes
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1
3
Wshed 1 Area 2.47 CN 71.64 PR 32.20 Wshed
2 Area 3.49 CN 65.01 PR 32.66 Wshed 3
Area 23.30 CN 68.70 PR 32.51
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Geometric Network
Geometric Network for Streams in Upper Guadalupe
Trace Downstream
Network Flag
Trace Upstream
Find Path
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Geo-processing
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Surface analysis

• Raster Models
• Perform simple algebraic calculations on raster
  cells
• Drainage Analysis using DEM
• Flow direction, flow accumulation, watershed
  delineation

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Runoff calculations
Cell by cell evaluations of mathematical functions
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Pollutant Loading Estimation
Load Mass EMC Runoff
Computation of pollutant load (fecal coliform) to
Galveston Bay in Texas.
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Drainage Analysis
75
77
79
85
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DEM
Flow Direction Grid
Contributing areas and stream definition
Stream Cell
Eight direction pour point model
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Zonal Stats Area, CN and PR
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Overview

• GIS and data representation
• Geodatabase design
• Vector and surface analysis
• 3D and visualization in GIS
• GIS and Modeling
• Case studies

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3D Representation of MODFLOW
Control volume for the model domain
Vertical dimension 75 meters
Each cell in the 2D representation is transformed
into a 3D object (Multipatch)
Example from Savannah River in Georgia
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3D HydroElement
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Rainfall and Streamflow Variations
29 hour duration, 15-minute interval
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Tracking Fecal Bacteria in Galveston Bay
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Overview

• GIS and data representation
• Geodatabase design
• Vector and surface analysis
• 3D and visualization in GIS
• GIS and Modeling
• Case studies

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GIS and Modeling

• Loose coupling
• Use GIS to extract input data and display output
• Model runs independent of GIS
• Tight coupling
• GIS and model are integrated in one system (eg.
  EPA Basins)
• Hydrologic Information Systems
• Framework for coupling

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Loose Coupling

• HEC-GeoRAS
• GIS interface for HEC-RAS
• cross-sections, reaches, bank-lines in GIS
• Creates geometry files
• Display Results in GIS

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Tight Coupling

• GIS and model are integrated within one system
  (eg. EPA Basins)
• Tool development in GIS to simulate hydrologic
  processes
• Dynamic Link Libraries
• Code development
• Must keep up with technology and model development

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Hydrologic Information System
A hydrologic information system is a combination
of geospatial and temporal hydrologic data with
hydrologic models that supports hydrologic
practice, science and education
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Connecting Arc Hydro and Hydrologic Models
Interfacedata models
GIS
HMS
HMS IDM
Geo Database
Arc Hydro data model
RAS
RAS IDM
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ArcGIS Model Builder
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Overview

• GIS and data representation
• Geodatabase design
• Vector and surface analysis
• 3D and visualization in GIS
• GIS and Modeling
• Case studies

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From a NEXRAD Map to a Floodplain Map Center for
Research in Water Resources
Component 3 Creating a Flood Inundation Map
Component 1 Importing NEXRAD data into
Geodatabase and Mapping to Watersheds
Component 2 Hydrologic Hydraulic Integration
based on common geographic framework
Hydrologic Model HEC-HMS
Hydraulic Model HEC-RAS
NEXRAD Data
Salado Creek, San Antonio
Rosillo Creek
Watersheds
NEXRAD Rainfall
Geographic Integration using Arc Hydro
Component 3
Process Operations using Arc 9 Model Builder
Component 1
Component 4
Component 4
Component 2
Component 4
Component 3 Floodmapping from HEC-RAS GIS SDF
File
Component 4 Geodatabase to HEC-DSS to Geodatabase
Flood Inundation Polygon
DEM
Cross Sections with Water Surface Elevations
Water Surface Raster
Time Series in HEC-DSS
Time Series in Geodatabase
HEC Data Storage System for Time Series
Research funded by The San Antonio River Authority
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Fish Habitat Modeling
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Hydraulic and Biological Data
Attribute Table
Bathymetry Points
Habitat Descriptions
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Summary

• GIS can be used to store and visualize any type
  of data (geospatial and temporal)
• Geodatabase Model for storing Data
• Vector and surface analysis in GIS help
  accomplish data processing, parameter extraction
  and simple calculations
• Hydrologic Information Systems provides a way to
  integrate simulation models with GIS using a
  standard protocol

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Courtesy Texas Water Development Board
Questions
Thank you

• David R. Maidment
• Tim Whiteaker