Modeling Urban Growth in Rockbridge County: The Risk to Rural Conservation Areas

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Modeling Urban Growth in Rockbridge County The
Risk to Rural Conservation Areas

• Charles Dietzel
• Duke University
• March 18, 2002

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Overview

• Overall Question
• Background
• County Facts
• Data
• Modeling Growth
• Results
• Conclusions
• Suggestions

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How Is Rockbridge County Growing?Are Rural
Conservation Areas At Risk To Urbanization?

• Population trends
• Land use/Land cover changes
• Modeling growth patterns

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1980s Rural Population Trends

• Decline in rural populations
• Recession
• Foreign industrial competition
• Farm crisis
• Lower retiree movement
• Overall negative growth

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1980s National Population
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1980s Population Trends
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1990s Rural Population Trends

• Increase in rural populations
• Stronger economy
• Recreational increase
• Stronger job market
• Overall positive growth

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1990s National Population
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1990s Rural Population Trends
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Rockbridge County Facts

• 610 Square Miles
• Growth
• 1980s
• 1990s
• Future

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Rockbridge Population and Growth
Source Central Shenandoah Planning District, UVA
Geostat Library
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Rockbridge Population and Housing
Source Central Shenandoah Planning District
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Rockbridge County Facts

• Citizen movement
• Imagine Rockbridge
• 2000 Publication
• More than 20 areas for conservation

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Conservation Areas

• 20 Natural Areas
• Defined by points

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Rural Conservation Areas
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Zoning District Densities
Source Rockbridge County Planning Department
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Current Zoning
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Data

• Spatial scale
• Temporal scale
• May 26, 1989
• May 20, 1992
• May 31, 1996
• June 21, 2001
• Ancillary GIS coverages

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Classification

• Agriculture
• Barren
• Deciduous
• Pine
• Urban
• Water

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Models

• Null Model
• Logistic regression
• Cellular
• Patch
• Mile

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1989 Land Use
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1992 Land Use
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1996 Land Use
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2001 Land Use
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Null Model

• Based on Transition rates
• Assumption of stationarity
• No spatial dependencies
• Only need current state?

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Overall Transition Matrix
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Urbanization Trends
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Predicted Change to Urban
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Change to Urban and Zoning
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Logistic Regression Models

• Risk value between 0 and 1
• Spatial and environmental variables
• Different scales of influence

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Variables

• Distance to roads
• Distance to streams
• Distance to buildings
• Slope
• Elevation
• Aspect

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Scales

• Pixel
• Patch
• Mile

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Predicted Change to Urban
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Predicted Change to Urban (patch size)
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Predicted Change to Urban (development size)
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Results

• Citizen were correct
• General Trends
• Range of Values
• Mean Overall Risk

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Results

• Most Endangered
• Irish Creek
• Devils Marbleyard
• Rapps Mill
• Least Endangered
• Brushy Hill
• Walkers Creek
• North Mountain Trail

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How Can Loss Of These Areas Be Prevented?
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Suggested Methods

• Urban Growth Boundary
• Conservation Overlay District
• Transfer of Development Rights
• Conservation Easements
• Fee Simple Acquisition

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Urban Growth Boundary

• Firm Boundary
• Clear Urban/Rural Distinction
• Promote Sustainable Development/Infill
• Preserve Natural Areas
• Reduce Natural Hazards

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Source City of San Jose Department of Planning,
Building, and Code Enforcement
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Conservation Overlay District

• Multi-purpose
• Environmental
• Scenic
• Tourism

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Source Town of Garner, NC
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Source Town of Garner, NC
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Transfer of Development Rights

• Transfer development
• Sending Areas
• Receiving Areas
• Benefits
• Drawbacks

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Source Dane County, Wisconsin, Planning and
Development Office
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Conservation Easements

• Deed restriction
• Term of restriction
• Retained Rights
• Benefits
• Drawbacks

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Fee Simple Acquisition

• Ownership
• Benefits
• Drawbacks

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Source San Juan County, WA Land Bank
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"There are not many things that you can do that
will still make a difference not just a year from
now, but in 100 years, but this really does."--
Augusta County Easement Donor
Source Valley Conservation Council, Staunton, VA