Kevin Behm – Addison County Regional Planning Commission

Community

Build-Out

Analysis

Nov 5, 2007

New techniques - for an old friend

Community Build-Out Analysis Development started in 1999 as a part of the Community Planning

Tools Demonstration Project funded by Sen. Leahy’s Office and administered by the Center for Rural Studies at UVM.

Center for Rural Studies has provided additional funding to improve the program over the past 6 years. The Vermont Agency of Transportation assisted in this version.

Operates as an extension to the ESRI GIS program ArcView 3.2

Public funding – the program is free, but support is limited

Community Build-Out Analysis The current version (v2.0) and a detailed manual are available as a

download from The Center for Rural Studies at UVM.

http://crs.uvm.edu/cpdp/buildout A new version (v.3.0) with innovative techniques is in beta testing

and will be available soon.

The new features include:

1. Mixed use zoning districts and mixed res/com buildings2. Open-space zoning concepts3. User defined timelines for build out scenarios4. Population projections using trend analysis5. User defined compact areas for development ‘seeds’

What is a Build-Out?

A build-out analysis predicts the maximum potential for development based on town policies and zoning bylaws as well as environmental or geographic constraints to development.

WHY? A planning tool to assess the consequences of existing and proposed planning and zoning practices.

1869 1942

1962 1977

1992 1995

Existing zoning

Build-out under existing zoning

Existing residential – 611 Potential development

with no development in wetlands, floodplain, or forest districts - 3263

DRAFT zoning

Low density district changed from 5 acre to 10 acre

Forest District changed to Conservation to include hilltops and steep slopes

Build-out under draft zoning

Potential residential development – 1546

vs. current zoning of 3263 units

Build-Out Status All parcel/zoning combinations are symbolized with a build-out result

No existing house and under the minimum

lot size ( 1 unit added)

Under the minimum lot size

Density removed using a layer

Density allowed but houses must be relocated off of layer

Density reduced using a layer and fewer houses shown

Compare build-out results - spatial

Development density changes Polygon symbology changes

Existing zoning Draft zoning

Methodology – Com/Industrial

Village/ Commercial Area

Min Lot Size .33 ac(14,520 sq ft)

Lot Coverage 75%Max Building Hgt 35 ftSq Ft / Parking Sp 200

Existing Development

Resulting Summary Table by Zone

Compare build-out results – export to spreadsheet

RA2 (2 ac)571

RA5 (5 ac)2472

RA1 (1 ac)199

WLD (25 ac)0

FOR (25 ac)0

FHA (25 ac)0

Draft zoning

RA-2 (2 ac)404

LDAD (10 ac)

993

RA-1 (1 ac)117

RA-1-V (1 ac)

33

CON-P (10 ac)

0

Existing zoning residential units – 3263

Draft zoning Residential units –1546

Existing zoning

Methodology – Data Needs

Uses existing town GIS dataZoningTax ParcelsExisting Development Points• Residential• Commercial• Industrial• Public ServiceExcluded parcel points

Natural Resource Information Data must be current or

updated for accuracy

Methodology – Basic Steps

A. Construct a table of each parcel’s acreage by zoning district

B. Determine existing parcels that are fully developed

C. Calculate potential new development allowed in each zone

Methodology – Next Level

Change minimum lot size of ASRR district to 5 acres from 10 acres

Methodology – Compare Tables

Potential units in the ASRR district increase from 181 to 617

Methodology – Operations

Build out operations on multiple layersRemoval of development potentialReduction of potentialIncrease development potentialA road frontage-based build out is also possible with a properly prepared road file

Mixed use zoning districts and mixed res/com buildings

Open-space zoning concepts

Open-space zoning concepts

Density-based or Set-Aside with bonus

Density – based example60 acre parcel in a 1 house/5 acre maximum density district

Typically provides for 12 houses on 5-acre lotsWith a minimum lot size of 2 acres –

12 homes can be placed on as little as 24 acres Leaving up to 36 acres open on this parcel

Open-space zoning conceptsTracking open-space acres

Time – based scenario requirements

Supply – Demand model Maximum build out is available supply Population projection is the demand over a certain time frame. Population is divided into households and per household estimates of

commercial and industrial land use are used. (these estimates are set by the user)

Spatial allocation of growth Where is growth likely in the community – mixed use areas vs. scattered development Placement of residential and commercial uses in a mixed use zone is determined by locations of existing development

Identify mixed-use areas as possible ‘seeds’ for future growth

Using Herfindal-Hirschman Index (HHI) – Daniel Rodriguez, Univ of North Carolina

Sum of each land use proportion squared

100% Res HHI = 1002 = 10,000

50% Res, 50% Com HHI = 502 +502 = 5,000

50% Res, 25% Com, 25% Ind HHI = 502 + 252 +252 = 3750

Establish a neighborhood around existing development and calculate

Identify mixed-use areas as possible ‘seeds’ for future growth

Review each land use proportion in the neighborhood

Identify mixed-use areas as possible ‘seeds’ for future growth

Transfer HHI and percentages to parcels

Query build out parameters to identify ‘compact areas’

Population Projections

Establish base year, interval and final year

Enter historic data for base period

Calculate population projections using trend extrapolation techniques

Review and Select Projection

Statistics are provided for evaluation

MAPE – Maximum Absolute Percent ErrorCRV – Coefficient of Relative VariationMean Error

Compare results – export to spreadsheet

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

Base Base Base Base Base Proj Proj Proj

1960 1970 1980 1990 2000 2010 2020 2030

HISTORICAL

LINEARREG

GEOMETRIC

PARABOLIC

MODEXPLM

GOMPERTZLM

LOGISTICLM

Time slice growth allocation

Compact If there are multiple compact areas

allocation is in order of density Parcels adjacent and within each

compact area are queryed for the highest density differential (ie. vacant parcels adjacent to fully developed parcels developed first)

Parcels selected for development based on best-fit of the number of units

Primary growth allocation via compact area vs. scattered

Scattered (Town-wide) Random choice of parcels

including those in compact areas

Time scenario results by time slice

Household units with HH units carried over to next time slice.

Commercial units with commercial sq ft carried over.

Industrial units with commercial sq ft carried over.

Parcels are built out completely so extra units must be carried over to the next time period

Time slice growth allocation75% Compact

50% Compact50% Town-wide

100% Town-wide

Next Steps for CBOA

1. Continue to use the program with communities.2. Work to improve the currency/accuracy of town data. 3. Improve the program with new ideas from users.4. Issues – move to ArcGIS or Open-Source5. Web-based?6. Funding partner? – please call.

Acknowledgements

Thanks to the Vermont USDA and Senator Leahy’s staff for originally supporting the Community Planning Tools Demonstration Project and to the Center for Rural Studies at UVM and the Vermont Agency of Transportation for providing development support.

In addition, we want to recognize the important land use decisions that are made by the volunteer boards and commissions in each of our communities. We sincerely hope that these tools will be an asset to their efforts.