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

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

Data Model Data Model based on based on Inventory of Inventory of data layersdata layers

Vector Data

(x1, y1)

(x2, y2)

(x4, y4)(x3, y3)

Point – pair of (x,y) coordinates

(x2, y2)

(x1, y1)

(x1, y1)

(x1, y1)

(x1, y1)

(x1, y1)

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.

064.0056 112.3213

Raster Data

1 2 3 4 5 6

1 2 3 4 5 6

1 2 3 4 5 6

1 2 3 4 5 6

1 2 3 4 5 6

1 2 3 4 5 6

Number of columns

Num

ber

of r

ows

Cell Size

Cell

Cell Value

Example, Digital Elevation Model

Raster Raster Vector Vector

PointPoint

LineLine

PolygonPolygon

VectorVector RasterRaster

Zone of cells

Triangulated Irregular NetworkEdge

Node

Face

How do we combine these data?

Digital ElevationModels

Watersheds Streams Waterbodies

An integrated raster-vector database

Overview






• Case studies

Geodatabase DesignGeoDatabase (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 classObject 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 betweenobjects linked by tracing pathof water movement

Arc Hydro Data Model

• A geospatial and temporal data model for water resources

HydroJunction

HydroEdge

Watershed

Arc Hydro framework

Personal Geodatabase

HydroEdge

HydroJunction Watershed Network Relationships

FeatureDataset

Overview






• 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

ReachHasCrossSectionsReachHasCrossSections

Calculations using vector attributes

70.68

3.23

49.301.6534.1702.6947.264.71898

AvgCN

51.32

3.23

49.366.3234.1753.3247.220.32898

AvgPR

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

1

2

3

Geometric Network

Network Flag

Geometric Network for Streams in Geometric Network for Streams in Upper GuadalupeUpper Guadalupe

Trace DownstreamTrace Downstream

Trace UpstreamTrace Upstream Find PathFind Path

Geo-processing

Surface analysis

• Raster Models– Perform simple algebraic calculations on

raster cells

• Drainage Analysis using DEM– Flow direction, flow accumulation, watershed

delineation

Runoff calculations

Runoff, Q (mm/yr)Precipitation, P

(mm/yr)

P

Q

Cell by cell evaluations of mathematical functionsCell by cell evaluations of mathematical functions

Pollutant Loading Estimation

Load Mass = EMC * Runoff

Runoff Load

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

Drainage Analysis

75 77 79 85 92

76 80 73 85 89

72 75 81 83 87

90 85 83 72 82

95 90 89 80 70

32

16

8

64

4

128

1

2

DEM

Eight direction pour point model

Flow Direction Grid Contributing areas and stream definition

Stream Cell

Zonal Stats: Area, CN and PR

Overview






• Case studies

3D Representation of MODFLOW

Vertical dimension ~ 75 meters Each cell in the 2D representation

is transformed into a 3D object

(Multipatch)

Control volume for the model domain

Example from Savannah River in Georgia

3D HydroElement

Rainfall and Streamflow Variations

29 hour duration, 15-minute interval

Tracking Fecal Bacteria in Galveston Bay

Overview






• 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

– Dynamic Link Libraries– Code development– Must keep up with technology and model development

Hydrologic Information System

Modeling

Geodatabase

A hydrologic information system is a combination of geospatial and temporal hydrologic data with hydrologic models that supports hydrologic practice, science and education

HMSIDM

RASIDM

Interfacedata models

HMS

RAS

GIS

GeoDatabase

Arc Hydrodata model

Connecting Arc Hydro and Hydrologic Models

Model

Process

Process

Process

ProjectData

ProjectData

ProjectData

DerivedData

DerivedData

DerivedData

Tool

Tool

Tool

(a) (c)(b)

ArcGIS Model Builder

Overview






• Case studies

From a NEXRAD Map to a Floodplain MapCenter for Research in Water Resources

Component 2

Component 4

Component 1

Component 4

Component 3

Component 3: Floodmapping from HEC-RAS GIS SDF File

DEM Cross Sections with Water Surface Elevations

Water Surface Raster Flood Inundation Polygon

Component 2: Hydrologic & Hydraulic Integration based on common geographic framework

Hydrologic ModelHEC-HMS

Hydraulic ModelHEC-RAS

Geographic Integration using Arc HydroWatersheds

Component 1: Importing NEXRAD data into Geodatabase and Mapping to Watersheds

NEXRAD Data

Component 4: Geodatabase to HEC-DSS to Geodatabase

Time Series in Geodatabase

Time Series in HEC-DSS

HEC Data Storage System for Time Series

FLOODPLAIN MAP

Component 4

NEXRAD Rainfall

Salado Creek, San Antonio

Rosillo Creek

Component 3: Creating a Flood Inundation Map

Process Operations using Arc 9 Model Builder

CRWRCRWRCRWR

Research funded by The San Antonio River Authority

Fish Habitat Modeling

Instream Flow

Decision Making

Hydrodynamic

Model

Habitat

Descriptions

Habitat

Model

GISRMA2 Biological

Sampling

Depth & velocity

Species groups

Criterion

Hydraulic and Biological Data

Bathymetry Points

Attribute Table

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

Questions

Courtesy: Texas Water Development Board

David R. Maidment

Tim Whiteaker

Thank you

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

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