GIS Modeling

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# GIS Modeling - PowerPoint PPT Presentation

GIS Modeling. Venkatesh Merwade, University of Texas at Austin. Interdisciplinary aquatic modeling workshop, July 21, 2005. 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 Modeling

Venkatesh Merwade, University of Texas at Austin

Interdisciplinary aquatic modeling workshop, July 21, 2005

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

Vector Data for Guadalupe Basin in Texas

Monitoring Points – USGS gaging stations

Stream Network – Low resolution NHD Flowlines

Watershed – 8 digit HUC units

Measure in ArcGIS

A PolylineMZ can store m and z at each vertex along with x and y coordinates.

64.0056

112.3213

0

Raster Data

Number of columns

Cell Size

Number of rows

Cell

Cell Value

Example, Digital Elevation Model

Raster  Vector

Vector

Raster

Point

Line

Zone of cells

Polygon

How do we combine these data?

Digital Elevation

Models

Streams

Watersheds

Waterbodies

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

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

Integrating Data Inventory using a Behavioral Model

Relationships between

of water movement

Arc Hydro Data Model
• A geospatial and temporal data model for water resources

Arc Hydro framework

HydroEdge

Personal

Geodatabase

Watershed

HydroJunction

Feature

Dataset

Network

Hydro

Edge

Hydro

Junction

Watershed

Relationships

Overview
• GIS and data representation
• Geodatabase design
• Vector and surface analysis
• 3D and visualization in GIS
• GIS and Modeling
• Case studies
Vector Analysis
• Attribute tools
• Join/relate, calculations
• Topology and Network analysis
• geometric networks and solvers
• Geo-processing
• Batch processing of geometries
Attribute Relationships

ReachHasCrossSections

Calculations using vector attributes

2

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

Geometric Network

Geometric Network for Streams in Upper Guadalupe

Trace Downstream

Network Flag

Trace Upstream

Find Path

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

Runoff, Q

(mm/yr)

Q

Precipitation, P

(mm/yr)

P

Runoff calculations

Cell by cell evaluations of mathematical functions

Runoff

EMC * Runoff

Computation of pollutant load (fecal coliform) to Galveston Bay in Texas.

32

64

128

16

1

8

4

2

72

95

76

90

75

85

90

80

81

73

83

89

83

85

80

72

82

89

70

87

Drainage Analysis

75

77

79

85

92

DEM

Flow Direction Grid

Contributing areas and stream definition

Stream Cell

Eight direction pour point model

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

Rainfall and Streamflow Variations

29 hour duration, 15-minute interval

Overview
• GIS and data representation
• Geodatabase design
• Vector and surface analysis
• 3D and visualization in GIS
• GIS and Modeling
• Case studies
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
Loose Coupling
• HEC-GeoRAS
• GIS interface for HEC-RAS
• cross-sections, reaches, bank-lines in GIS
• Creates geometry files
• Display Results in GIS

Tight Coupling

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

Modeling

Geodatabase

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

Connecting Arc Hydro and Hydrologic Models

GIS

Interfacedata models

HMS

HMS

IDM

Geo

Database

Arc Hydro

data model

RAS

RAS

IDM

Model

Process

Process

Derived

Data

Project

Data

Tool

Derived

Data

Tool

Process

Project

Data

Derived

Data

Tool

(a)

(b)

(c)

Project

Data

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

FLOODPLAIN MAP

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

Rosillo Creek

Watersheds

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

Criterion

Depth & velocity

Species groups

Habitat

Hydrodynamic

Habitat

Model

Model

Descriptions

RMA2

Biological Sampling

GIS

Instream

Flow

DecisionMaking

Fish Habitat Modeling
Hydraulic and Biological Data

Attribute Table

Bathymetry Points

Habitat Descriptions

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

Courtesy: Texas Water Development Board

Questions

Thank you

• David R. Maidment
• Tim Whiteaker