Town of Gilford, New Hampshire

Transcription

1 Town of Gilford, New Hampshire Technical Report: Build-Out Analysis Prepared by: Lakes Region Planning Commission 3 Main Street, Suite 3 Meredith, NH August 2003 Funding for this report was provided, in part, with Targeted Block Grant funds administered by the New Hampshire Office of State Planning

2 TABLE OF CONTENTS INTRODUCTION.2 METHODOLOGY 2 BUILD-OUT INPUTS DETAILS DATA DEVELOPMENT.. 4 BUILDING CONSTRAINT LAYERS....5 OVERLAY ANAYLISIS AND BUILD-OUT CALCULATION..8 RESULTS OF THE MODEL.. SUMMARY OF THE DATA.. APPENDIX A: MAP PRODUCTS. APPENDIX B: LOT EXCEPTIONS..25 APPENDIX C: DATA DEVELOPMENT..27 1

3 Introduction Build-Out refers to the time and circumstances whereby, based on a set of restrictions, no more building growth may occur. For our purposes it means the point at which, under current zoning requirements, no more house lots may be created in a municipality. It is the point at which lots have been subdivided to the minimum size allowed and there is no more developable land. The Lakes Region Planning Commission (LRPC) has performed a Build-Out analysis for the Town of Gilford at the request of the Town. The Town of Gilford is interested in predicting the development potential for existing lots within the Town. The Town may use the results of the build-out for planning and tracking land use and development. LRPC staff performed the build-out analysis using Geographic Information Systems (GIS). LRPC developed the build out methodology with direction provided by the Gilford Town Planner. This report summarizes the methodology and findings of the LRPC in its performance of the build-out analysis. Methodology Build-Out Steps The Build-Out was performed following these general steps: 1. Acquire and develop a polygon composite Tax map layer. 2. Develop Natural Building Constraints (non-buildable areas) layers. 3. Link Assessing database to Tax map layer. 4. Develop Zoning layer. 5. Union Tax Maps, Zoning, and Constraints layers for Build-Out layer. 6. Summarize each lot by buildable and non-buildable area. 7. Calculate number of potential build-out units & lots per existing lot based on zoning requirements. 8. Report the number of build-out units & lots by zone.* 9. Calculate total number of additional housing units and potential population growth, reporting numbers by potential seasonal and resident units.*. Produce maps to illustrate the relative developability of existing lots. * The data for these steps is reported in a spreadsheet. Meetings Over the course of the project, LRPC met with the Town several times to discuss the project. In early May of 2003 LRPC presented preliminary build-out results to the Gilford Planning Board members and Town Planner and obtained feedback. Corrections to data layers were noted. 2

4 June 9, 2003 LRPC presented further edits and build-out results to the Town. Further feedback was received from the Town, including a request to provide a version of the build-out analysis using 25%+ slopes rather than %+ slopes. Various informal meetings, correspondences, and phone conversations took place between LRPC and the Town Planner during the project period (July 2002-July 2003). Build-Out Inputs Details Zoning Requirements Crucial to a Build-Out analysis is the feasibility of modeling zoning requirements. This study used the minimum allowable lot size and minimum contiguous buildable area per lot by zone to determine the build-out units and lots. Certain zoning requirements are too site specific to be able to incorporate into the analysis. An example of this would be Building Setbacks. Since the build-out is really a matter of aggregating and dividing land areas, while not knowing the real site design potential of a subdividable lot, the area removed for building setbacks cannot be pre-determined. Table 1 lists the zoning requirements for the Town of Gilford that were used in developing this study. Table 1 Zoning requirements All zoning districts require a minimum buildable area of 1 acre. The Island Residential and the Natural Resource Residential Zones have a minimum lot size of 2 acres, while all others have a minimum lot size of 1 acre. The Gilford Village Historic District (an Overlay District) requires a minimum lot size of 2 acres as well as a minimum buildable area of 2 acres regardless of zoning district. Frontage requirements were not addressed in this study, however a town-supplied percentage adjustment was used to account for land lost to construction of potentially needed subdivision roads. The figure provided by the town was 3% loss for subdivisions of less than acres and % loss for subdivisions of acres or more. 3

5 Natural Building Constraints According to the Town of Gilford Zoning Ordinance Buildable area shall not include land which is wetlands as defined by Section.2, prime agricultural land or agricultural land of statewide importance as classified by the Federal U.S. Soil Conservation Service, or land having a slope greater than fifteen percent (%). (Article 5.1.1, p. 48 3/14/00). Additionally, Conservation Lands were used as a building constraint. GIS layers were created to represent these areas using the best available sources. These layers are discussed in more detail in the Data Development section. Data Development Tax Parcel Polygon Development An important GIS data layer to be developed for the project is a polygon composite tax map. The Town was able to provide the digital files used to produce the Town s tax maps in CAD drawing file format. While the tax maps were in a digital format, they were not readily convertible to a polygon layer. Much work needed to be done to develop this layer. Joining the Assessing Database Merging the Assessing database with the Tax Parcel polygon layer yields information that is vital to the build-out analysis. Gaining this link populated the tax parcel layer with fields from the Assessing database, which is necessary for developing a Build-Out. Each lot is coded with for the following attributes: Zoning District Existing Unit (or not) If lot is associated with condo units If lot is owned by the Town of Gilford (and presumed to stay undeveloped) Every effort was made to identify each parcel of land in the town records. There were, however, a small number of parcels (>2%) for which complete information was not available (See Appendix B). Building Constraint Layers Soils Based Layers 4

6 Many of the natural building constraint layers for the analysis could be derived from soil maps. Unfortunately, GIS soil data for Gilford was not available at the time of this analysis. Therefore, LRPC obtained and digitized sheets from an unpublished revision to the Belknap County Soil Survey for much of the Town s area and digitized the 1968 Belknap Soil Survey for the remainder of Gilford. Soil attributes for the different sections had to be obtained separately and applied for use. The soils were created and attributed as separate shapefiles, but were later merged together, forming a single PCArcInfo coverage for use in the overlay analysis. While the use of County Soil Survey data at the parcel level is inappropriate, having no alternative, this data had to be used. Figure 1 Soil Data Soil Data Sources The following coverages were derived from the soils coverage of Gilford; each are considered as non-buildable in the Build-Out: Very Poorly and Poorly Drained Soils - these soil types were used to model the wetland areas of Gilford. Soils with associated slopes of greater than % - these soil types were used to model the steeply sloped areas of Gilford, they most often have a D or E within their soil unit symbol. 5

7 Soils with associated slopes generally greater than 25% - these soil types were used to model the steeply sloped areas of Gilford, they most often have a E within their soil unit symbol. The E slopes were used exclusively as steeply sloped areas in a second version of the Build-Out analysis. Prime Farmland Soils - these soil types are nationally recognized as important agricultural soils. They are protected against development in Gilford. Agricultural Soils of Statewide Importance - these soil types are recognized as important agricultural soils within New Hampshire. They are protected against development in Gilford. Other Non-Buildable Areas 0 -Year Floodplains deemed non-buildable as part of the Wetlands District. Areas of the 0-year floodplains were digitized by LRPC from available Federal Emergency Management Agency Flood Insurance Rate Map (FIRM) for the Town of Gilford. Conservation Lands Lots restricting development with conservation easements. These were created by comparison of GRANIT (NH State GIS) NH Statewide conservation lands data layer with the tax parcel layer of Gilford. GRANIT Conservation Lands were remapped to better fit the Gilford Tax parcels. Areas of parcels outside of conservation easement were edited accordingly, allowing areas outside of the conservation easements to be considered for potential development. Figure 2 Matching easements to parcels 6

8 Editing Conservation Lands to match Gilford Parcels Differences in Lots and Units In most cases it is assumed that there will be 1 unit for each lot. By this logic, build-out units should equal build-out lots. However exceptions do exist. These occur for lots that contain condominium units. The analysis assumes that all lots with condominiums are currently at build-out. For these lots, the number of units will outnumber the number of lots. Exceptions also occur for lots that are deemed to be Town-owned and undevelopable, which will not experience additional unit or lot development. 7

9 Overlay Analysis and Build-Out Calculation Coverage Union Once the development of the necessary datasets was completed, overlay analysis to identify development potential could be performed. Overlay analysis is a software procedure to combine the various data layers together to make spatial comparisons. For Build-Out analysis it is used to determine the buildable areas per lot. This was accomplished by using the Union command in PCArc/Info software macro. Union combines two polygon coverages and retains the attributes from both input layers in an output coverage. The following diagram illustrates the union process used in the buildout. Figure 3 The GIS Overlay process SOILS WETLANDS, STEEP SLOPES, FARMLAND SOILS FLOOD PLAINS CONSERVATION LANDS GIS OVERLAY PROCESS A series of union overlays are performed to incorporate the various mapped components into a unified GIS layer containing Tax Lot, Zoning, and development constraint attributes. HISTORIC DISTRICT TAX PARCELS BUILDOUT 8

10 Build-Out Frequency File A frequency database file was produced to summarize the Build-Out layer attributes per Lot. The frequency file forms the informational basis for making a series of decisions and calculations to yield an estimate of the total number of lots and units that could be created from the subdivision of each existing lot. While each tax lot might be fragmented by non-buildable land into many separate polygons, the frequency file summarizes the overall buildable area per lot and the total area per lot into a single record for each lot. Results Spreadsheet An MS-Excel workbook file was created to calculate the final values of the Build-Out and to cross-tabulate the results Town Edits to Results Providing the results in an MS-Excel workbook enables the Town of Gilford to edit the Build-out values in the DATA worksheet to improve the accuracy of the results table. The Town may wish to apply local knowledge or assumptions to the Build-Out results. If any of the input values are edited, the final table will change. Altering these values for any lot will change the results per zoning district in the RESULTS sheet. 9

11 Results of the Model Using Slopes greater than % The following tables summarize the results of the Build-Out analysis. These tables were derived from the overlay analysis of the existing tax parcels with the natural building constraints datasets as earlier defined. This set of tables used soils sloped greater than %. Table 2 - Build-Out By Zone Table (using Slopes greater than %) EXIST- ING BUILD- % of Potential ADDITION- Lots LOTS OUT LOTS AL LOTS Subdivided EXIST- ING UNITS BUILD- OUT UNITS % of ADDITION- Potential AL UNITS Units Built ZONE C TOTAL % % Not Historic District % % Historic District % % I TOTAL % % Not Historic District % % Historic District % % IR TOTAL % % Not Historic District % % Historic District % % LR TOTAL % % Not Historic District % % Historic District % 7 70% NRR TOTAL % % Not Historic District % % Historic District % % PC TOTAL % % Not Historic District % % Historic District % % RC TOTAL % % Not Historic District % % Historic District % % SFR TOTAL % % Not Historic District % % Historic District % % TOTAL % ### %

12 Table 2 indicates that there is much potential subdivision that could occur in the three Commercial Zones and the Industrial Zone. Only the Resort Commercial is more than 50% subdivided, and the number of units built is at 70% of the maximum. Table 3 reports the number of additional residential units in the residential zoning districts. It includes a breakdown of Seasonal units and Resident units, which was figured using the Census 2000 figure of 33.1% Seasonal residential units for Gilford. Table 3 Potential Housing Units (using slopes >%) Housing Units Total Potential Zoning District Additional Units Seasonal Resident IR LR NRR PC RC SFR All Residental Zones Table 4 reports the number of additional Seasonal and Resident persons based upon the number of additional units as reported in the previous table. The figures are based on The NH Office of State Planning standard of 2.4 persons per household. Table 4 Potential Population (using slopes >%) Population Zoning District Total Seasonal Resident IR LR NRR PC RC SFR All Residental Zones The majority of existing lots are in the SFR Zone. The greatest potential for subdivision and development in terms of volume are found in the Limited Residential and Single Family Residential (SFR), with each zone having more than one thousand new

13 subdivisions possible. The data also indicate that the Island Residential (IR) and SFR Zones have each reached more than 50% subdivision and development of housing units, with Island Residential being over 70% in both categories. Figure 4 - Comparison of Steep Slopes Soils Sloped greater than % Soils generally Sloped greater than 25% Approx:,468 Acres Approx: 6,942 Acres Using Slopes generally greater than 25% The following tables summarize the results of the Build-Out analysis using an alternative method. Due to the smaller base map scale of the county soil survey, and its lower precision relative to the Tax maps, the Town of Gilford was interested in seeing the results of the Build-Out Analysis performed using soils sloped generally greater than 25% instead of soils sloped greater than %. The following tables were derived from

14 the overlay analysis of the existing tax parcels with the natural building constraints datasets as earlier defined, but this set of tables used soils sloped greater than 25%. Table 5 - Build-Out by Zone Table (using Slopes greater than 25%) ZONE EXISTING LOTS BUILD- OUT LOTS ADDITIONAL LOTS % of Potential Lots EXISTING Subdivided UNITS BUILD- OUT UNITS ADDITIONAL UNITS % of Potential Units Built C TOTAL % % Not Historic District % % Historic District % % I TOTAL % % Not Historic District % % Historic District % % IR TOTAL % % Not Historic District % % Historic District % % LR TOTAL % % Not Historic District % % Historic District % 31 52% NRR TOTAL % % Not Historic District % % Historic District % % PC TOTAL % % Not Historic District % % Historic District % % RC TOTAL % % Not Historic District % % Historic District % % SFR TOTAL % % Not Historic District % % Historic District % % TOTAL % % Table 5 lists the number of units and lots at Build-Out per zoning district. It includes a break down for lots or sections of lots within the Gilford Village Historic District. Also listed are the figures for Existing Lots, Existing Units, Additional Lots and Additional Units per zoning district. Table 6 reports the number of additional residential units in the residential zoning districts. It includes a breakdown of Seasonal units and Resident units, which was figured using the Census 2000 figure of 33.1% Seasonal residential units for Gilford.

15 The data in these tables indicate that raising the limits for steep slopes to >25% would result in a slight increase in Commercial and Industrial lots and units, with the greatest numerical increase in the Resort Commercial Zone (an additional 144 lots and units). In terms of Residential Zones, increasing the steep slope limitation would result in an additional 21 potentially developable lots, a 45% increase. More than a thousand additional lots could be developed in the Limited Residential Zone. Table 6 Potential Housing Units (using slopes >25%) Housing Units Total Potential Zoning District Additional Units Seasonal Resident IR LR NRR PC RC SFR All Residental Zones Table 7 reports the number of additional Seasonal and Resident persons based upon the number of additional units as reported in Table 8. The figures are based on The NH Office of State Planning standard of 2.4 persons per household. Table 7 Potential Population (using slopes >25%) Population Zoning District Total Seasonal Resident IR LR NRR PC RC SFR All Residental Zones

16 Summary of Data The purpose of a Build-Out Analysis is to present the Town with a model of their community and its potential for growth. On its first level the report gives a clear picture both of how much of the municipality has been developed as well as where that development has occurred. The predictive power of the Build-Out Analysis allows Town Planners to go a step beyond by exploring how much development could occur under current zoning and where that growth might be experienced. The third level of use for this Build-Out is as a working tool. The database can be updated as changes occur. This can be reflected in the rest of the Build-Out Analysis. This Build-Out Analysis assumes no further development on natural features such as wetlands and steep slopes, as well as on restricted areas such as prime farmland and conservation lands. Two versions of the data were developed reflecting the Planning Board desire to explore the impact on development of altering the steep slope limitation. The current zoning restrictions on lot size and contiguity were applied to each lot in the town. This resulted in figures indicating the potential number of lots and housing units that could be created in the Town of Gilford under current zoning and where such development could occur. Currently there are 3987 lots in Gilford and 78% of them have been built upon. Under current zoning ordinances, there is the potential for an additional 4655 lots. If the steep slope limitation were raised to >25%, then the number of potential additional new lots would increase to A majority of the existing Commercial and Industrial lots in Gilford have been built upon, however, with current zoning there is a great deal of potential for subdivision and new construction. The same pattern exists for both the Professional Commercial Zone, however, the Resort Commercial Zone is now 70% built out. Gilford has four Residential Zones, three of them have portions in the Historic District. The Historic District is very nearly built out. Seventy-eight percent of the remaining Residential areas in Gilford have been built upon. Under current zoning, there is a great deal more subdivision that could occur, especially in the Limited Residential and Natural Resource Residential Zones. With the present slope limitation, 46% of the lots in Gilford have been subdivided. If the limit on slopes were raised to >25%, this could result in an additional 21 lots, the majority in the Limited Residential Zone. According to the US Census Bureau, the population of the Town of Gilford in 2000 was The New Hampshire Office of State Planning s Population Projections indicate a 2005 population of 7380, rising to 7950 by 20 and a total of 8950 residents in The Town of Gilford does have a relatively large seasonal population (33.1%) and this is reflected in the figures. If the Town were to reach Build-Out with the current zoning, a population of 79 residents is indicated, while opening up some of the steeper slopes to development could accommodate more than,000 residents in the Town of Gilford.

17 APPENDIX A. Map Products 1. Zoning Districts Map 2. Lots with Existing Development Map 3. Development Constraints Map (greater than % slopes) 4. Build-Out Units and Non-Buildable Areas (greater than % slopes) 5. Build-Out Units Map (greater than % slopes) 6. Development Constraints Map (greater than 25% slopes) 7. Build-Out Units and Non-Buildable Areas (greater than 25% slopes) 8. Build-Out Units Map (greater than 25% slopes)

18 BUILD OUT ZONING MAP TOWN OF GILFORD Zoning District Natural Resource Residential Limited Residential Single Family Residential Resort Commercial Professional Commercial Commercial Industrial Island Residential Historic District Miles June 5, 2003 NOTE: Zoning Districts on this map were derived from the Town Assessing Database. Tax lots reflect the zone which they are recorded in the Towns Assessing Database.

19 LOTS WITH EXISTING DEVELOPMENT TOWN OF GILFORD Lot With Existing Building (1 or More Units) Miles June 5, 2003

20 DEVELOPMENT CONSTRAINTS TOWN OF GILFORD Wetland Soils Farmland Soils 0 Year Floodplain Conservation Land Town Owned Land (Protected) Soils Sloped Greater Than % Miles June 5, 2003

21 Build-Out Units and Non-Buildable Areas with Number of Potential Units for Residential Zones Town of Gilford (Slopes Greater Than % Version) 5 label of: Number of Potential Units (2+ Potential Lots) 66 Buildable Areas Non-Buildable Areas 41 consisting of the following: Conservation Lands -(GRANIT Database) 0 Year Floodplain Very Poorly Drained & Poorly Drained Soils Prime Farmland Soils & Farmland Soils of Statewide Significance Soils with 'D' & 'E' Slopes - greater than % slope Potential Number of Units are Labeled for lots yielding over Units at Build Out Miles 62 June 5, 2003 NOTE: This map does not consider the configuratoin of Existing Development per existing Lot. Lots that contain multiple condo units are considered to be 'built-out' on this map and the number of potential units = the number of existing units for these lots.

22 BUILD-OUT NUMBER OF POTENTIAL UNITS TOWN OF GILFORD (Slopes Greater Than % Version) 66 Potential Number of Units at Build Out (All Zones) Potential Number of Units are Labeled for lots yielding over Units at Build Out Miles June 5, NOTE: This map does not consider the configuratoin of Existing Development per existing Lot. Lots that contain multiple condo units are considered to be 'built-out' on this map and the number of potential units = the number of existing units for these lots.

23 DEVELOPMENT CONSTRAINTS TOWN OF GILFORD Wetland Soils Farmland Soils 0 Year Floodplain Conservation Land Town Owned Land (Protected) Soils Generally Sloped Greater Than 25% Miles June 5, 2003

24 Build-Out Units and Non-Buildable Areas with Number of Potential Units for Residential Zones Town of Gilford (Slopes Greater Than 25% Version) label of: Number of Potential Units (2+ Potential Lots) 5 3 Buildable Areas 19 Non-Buildable Areas 47 consisting of the following: Conservation Lands -(GRANIT Database) 0 Year Floodplain Very Poorly Drained & Poorly Drained Soils Prime Farmland Soils & Farmland Soils of Statewide Significance Soils with 'E' Slopes -generally greater than 25% slope Potential Number of Units are Labeled for lots yielding over Units at Build Out Miles June 5, 2003 NOTE: This map does not consider the configuratoin of Existing Development per existing Lot. Lots that contain multiple condo units are considered to be 'built-out' on this map and the number of potential units = the number of existing units for these lots.

25 BUILD-OUT NUMBER OF POTENTIAL UNITS TOWN OF GILFORD (Slopes Greater Than 25% Version) 3 Potential Number of Units at Build Out (All Zones) Potential Number of Units are Labeled for lots yielding over Units at Build Out Miles June 5, NOTE: This map does not consider the configuratoin of Existing Development per existing Lot. Lots that contain multiple condo units are considered to be 'built-out' on this map and the number of potential units = the number of existing units for these lots.

26 APPENDIX B. Lot Exceptions Joining the Assessing Database The Town of Gilford provided a CD-ROM with selected fields from the Assessing database as of August 19, The database was provided in an Excel spreadsheet format. This was converted to a database (.dbf) table format for processing. Merging the Assessing database with the Tax Parcel polygon layer yields information that is vital to the build-out analysis. Gaining this link populated the tax parcel layer with fields from the assessing database necessary for build out. The following attributes were extracted per lot for Build-Out use: Zoning District Existing Unit (or not) If lot is associated with condo units (Use = 7 ) If lot is owned by the Town of Gilford (and presumed to stay undeveloped) The Assessing database was joined to the tax parcel layer using the PID as the relate field, as this had been established in each table for this purpose. While most lots joined the database, there were many rejects. Several iterations of joining the Tax Parcels to the Assessing database had to be made along with additional PID editing and evaluation to eliminate mislabeled lots. Use was made of the CAD files to visually interpret the map and lot numbers for the un-joined lots. It was found that many records did match between the parcel coverage and the Assessing database. Many records in the Assessing database were coded with a PID, which followed a different format than most of the PID values. To correct this, whenever possible, the parcel polygon coverage was edited to match the Assessing database. A complete match was never fully accomplished due to some lots on the tax maps being unlabeled. Join Errors Approximately 73 records were found to be lots that were labeled on the maps, but were not found in the assessing file. In these cases, a link could not be established to the assessing database. Many of these could possibly be known as different lot numbers in the Assessing database, the maps could be out of date. The Built or Un-built status of each of these lots was observed from digital aerial photos taken in The Zoning District for these lots were inferred from the surrounding lots. Out of these records, there were lots where the existing tax maps are missing Map/Lot numbers for lots. The PIDs for these unlabeled tax parcels was coded in the format E#ERROR?U, where the # represents a sequential number to distinguish the lot. The last character of the unique 25

27 identifier is either U or B, to represent Unbuilt or Built respectively. (These records are listed below.) ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' 'EERROR?U' 'EERROR?U' 'E1ERROR?U' 'E2ERROR?B' 'E3ERROR?B' 'E4ERROR?U' 'E5ERROR?U' 'E6ERROR?B' 'E7ERROR?B' 'E8ERROR?U' 'E9ERROR?U' This table lists the PIDs found in the Tax Map coverage that do not have a clear match in the Assessing database. These occurred due to the following reasons: 1. Map and Lot on map has NO match in the Tax database may be due to Tax maps being out of date in comparison to the tax database. 2. Matches to many -Condo unit lots 3. No Map and Lot number on the tax map. These were given a PID for the analysis in the format of: E#ERROR?U, to distinguish these lots. The last letter is 'U' or 'B' for Unbuilt and Built based on Air photo inspection. 4. Map and Lot numbers for lot has no link to assessing database as the lot may contain Condominiums which each have a unique PID that are taxed independently. 26

28 Appendix C. Data Development Tax Parcel Polygon Development LRPC converted the CAD files into a polygon composite tax layer in ESRI Shapefile format. Once polygons had been developed, they needed to be coded by a parcel identifier (PID) code in order to relate to the Town s assessing database. The Town of Gilford provided an AmeriCorps member to manually code each lot using ArcView GIS software and a hardcopy set of the Town tax maps. This work was done at the Town of Gilford Planning Department. This shapefile was returned to LRPC for further processing. LRPC used Arc/Info software to convert the shapefile into a topologically correct polygon coverage to prevent errors associated with overlapping lots, or gaps between lots. Once topology was established the coverage was converted into PCArcInfo for merging with the Town s Assessing database and for GIS overlay analysis. Union The initial stages of unioning combines the Natural Building Constraint layers together. Once unioned, the resultant layer is dissolved based upon constrained areas. All nonbuildable areas, whether wetland, steep slopes or otherwise are coded as Constrained. All adjacent constrained areas are merged together. The unioned, dissolved constraints layer is then unioned with the Tax parcel layer. The ultimate coverage produced by the unioning process is the Build-Out layer. This coverage contains the following attributes: 1. PID - unique parcel identifier used by Assessing Database 2. ZONE Zoning District code 3. HISTD - Historic District set to Y or N; Yes if within or No if not within. 4. CONSTR - Non-Buildable land Y or N. 5. ACRES - acreage 6. NLOTS - number of 1 acres lots per buildable polygon. Set to 0 for nonbuildable. Build-Out Frequency File A frequency database file was produced to summarize the Build-Out layer attributes per Lot. The frequency file forms the informational basis for making a series of decisions and calculations to yield an estimate of the total number of lots and units that could be created from the subdivision of each existing lot. While each tax lot might be fragmented by non-buildable land into many separate polygons, the frequency file summarizes the overall buildable area per lot and the total area per lot into a single record for each lot. 27

29 Added to the frequency file were several attributes generated from the Assessing database. This was accomplished by joining database tables by PID containing the following attributes: 1. BUILT Set to Y or N ; set to Y if a building value exists for the lot in the assessing database. For lots missing from the Assessing database, it is set to Y for those lots in which development is visible on 1998 aerial photography. 2. TWN_UD - Set to Y or N ; set to Y if the lot is a Town owned lot that was not on the list of developable lots provided by the Town Planner. 3. USE - Set to 7 if there are condominium units on the lot. The Assessing Database uses the value CONDNUM the number of condo units on the lot. 5. MAPNDB - set to Y if the lot is not found in the Assessing database. Additional attributes were added for reporting build-out values. The following attributes were added to the Build-Out Frequency file: 1. EXISTING Holds the number of existing Units (houses, commercial or industrial buildings and condo units) 2. FINLCT Holds the number of Units at Build-Out. 3. ADDTL Holds the number of additional Units that would be added to existing units to reach Build-Out. 4. BO_LOTS - The number of lots at Build-Out. 5. ADJBOLOT The number of lots at Build-Out adjusted by Town supplied adjustment factor to account for land lost to subdivision roads to gain frontage. This factor was 3% loss for subdivisions of less than acres and % loss for subdivisions of more than acres. Build-Out Calculation Macro A macro was developed in PCArc/Info SML to process the Build-Out Frequency File to calculate the number of build-out lots per existing lot, given zoning requirements and area of developable land. Development of a decision and calculation program was necessary considering the amount and iterative nature of the calculations to be made. Calculation of the number of build-out lots followed this logic. 1. BO_LOTS for NRR and IR zones calculated to the Lesser of ACRES divided by 2 (integer division) and NLOTS divided by 2. Thus, the Build-Out lots for lots in zones with a 2 acres minimun lot size, 1 acre buildable requirement meet the requirements. All other zones, BO_LOTS = NLOTS (# buildable 1 acre areas per lot) 28

30 2. BO_LOTS for HISTD = Y (Historic District Lots) calculated to NLOTS divided by 2. Thus, the build out lots per existing lot in the Historic District is equal to the number of buildable areas that are at least 2 acres in size. 3. ADJBOLOT is set to BO_LOTS adjusted by Town supplied adjustment factor. This is done by subtracting 3% of the BO_LOTS value for all subdivisions of less than acres; adjusted by % for BO_LOTS acres or more. 4. EXISTING calculated to 1 if BUILT = Y ; calculated to CONDNUM if USE = 7, thus EXISTING equals the number of buildings or condo units found on the lot. 5. If condos are found on the lot, ADJBOLOT = 1 and FINLCT = EXISTING. Thus all lots that contain condos are considered to be Built-Out at their current number of units. 6. If TWN_UD = Y, then ADJBOLOT = 1 and FINLCT = EXISTING. 7. ADDTL (additional Units) is set to FINLCT (Build-Out Units) EXISTING (Units). 8. For any ADJBOLOT (Adjusted Build-Out Lot) now = to 0, ADJBOLOT is set to 1 lot. FINLCT is set to 1 (unit). If the lot exists, it either meets zoning requirements or is grandfathered. Results Spreadsheet The final step of the Build-Out Calculation Macro is to dump the database into an ASCII text file. An MS-Excel workbook file was created to calculate the final values of the Build-Out and to cross-tabulate the results. The spreadsheet contains a macro to read in the ASCII version of the calculated Frequency table. The spreadsheet, BOTAB_DE.XLS (or BOTAB_E.XLS, for E slopes only), adds a few columns to the database to automate calculation of final results and facilitates cross-tabulation. The Build-Out MS-Excel workbook is comprised of the following worksheets 1. RESULTS Table of Build-Out results per Zoning District and for within Historic District or not. The Table gives Existing Lots; Existing Units; Build-Out Lots; Build-Out Units; Additional Lots; and Additional Units. It also contains tables that give Build-Out population estimates and Seasonal & Resident housing units at build-out. 2. PIVOT TABLE Contains cross-tabs for the Build-Out results per zone. Also contains explanations of table values. 3. DATA -The Build-Out frequency database, with additional columns added to calculate additional number of lots per existing lot. 4. CONDO LOTS Lists PID values for all lots with condominiums. Contains a cross-tab that gives the number of condo lots and condo units per zone. 5. TOWN_UNDEV Lists PID values for all lots that are owned by the Town that were not listed by the Town as developable. 6. MAPnotDBF Lists PID values for all lots found on Tax coverage that do not link to the Assessor s database. 29

31 Town Edits to Results Providing the results in an MS-Excel workbook enables the Town of Gilford to edit the Build-out values in the DATA worksheet to improve the accuracy of the results table. The Town may wish to apply local knowledge or assumptions to the Build-Out results. If any of the input values are edited, the final table will change. Altering these values for any lot will change the results per zoning district in the RESULTS sheet. Section of DATA sheet of the Build-Out Excel Workbook. The DATA sheet contains two yellow columns that can be edited to refine build-out results. The ADJBOLOT column contains the number of potential build-out lots per existing lot. The Edited FINLCT column contains the number of potential build-out units at build-out. These numbers would typically match each other, except in the case of condominium lots or lots that restrict development, such as Town owned undeveloped lots or whole lots within conservation easements. An example may be that the Town assumes that a certain property will never be developed. The Town could edit the Edited FINLCT (units) and the ADJBOLOT (lots) columns could to say 0. This, in-turn would decrease the number of Build-Out units and lots for that zoning district, and for the whole Town. As development occurs, the Edited FINLCT and ADJBOLOT fields could be edited in the DATA worksheet to reflect reality. This enables the Town to easily adjust the Build-Out analysis as development occurs over time. The DATA sheet also contains two pink columns that identify condominium lots. The USE column is set to 7 if the lot contains condominium units. The CONDNUM column reports the number of condo units per lot. If an existing lot should be identified as a condo lot, the USE column could be edited to say 7 for that lot and the CONDNUM column could be edited to say the number of condo units for the lot. Editing these values will recalculate the cross-tabs which contribute to the results per zoning district on the RESULTS sheet. 30

32 Differences in Lots and Units In most cases it is assumed that there will be 1 unit for each lot. By this logic, build-out units should equal build-out lots. However exceptions do exist. These occur for lots that contain condo units. The analysis assumes that all lots with condos are currently at buildout. For these lots, the number of units will outnumber the number of lots. Exceptions also occur for lots that are deemed to be Town-owned and undevelopable, which will not experience additional unit or lot development. Though some of these lots do have existing units on them, many do not. For these, the number of lots will outnumber the number of units. Because of these exceptions, the sum of Additional Lots and Additional Units per zoning district will not always appear straightforward. To explain the difference between Number of Units to Number of Lots at Build-Out: The extra units associated with lots with condos comprise much of the difference. The difference between the number of condo units and the number of lots with condos is determined. The number of Town owned and undevelopable lots with 0 existing units should be subtracted from this number to adjust for the lots that have no existing units and will not have any additional units. The difference of these numbers equals the difference between build out units and build-out lots. To explain the difference between Number of Additional Units to Number of Additional Lots at Build-Out: The number of existing lots with 0 units on them is determined. The difference between this number and the number of Town owned and undevelopable lots with 0 existing units equals the difference between additional units to additional lots at Build-Out. The existing lots with 0 units on them are inclusive of the Town owned and undevelopable lots. The difference must be determined because Town owned and undevelopable lots with 0 existing lots will never have a unit on them. Conclusions This type of build-out analysis can help the Town of Gilford to predict and plan for future development. Existing lots can be prioritized for development or for conservation. Due to zoning requirements, ownership status and geography, the largest land lots are not necessarily the most developable. This effort allows us to make an estimate of the number of potential lots and units of Town, using available GIS data layers. GIS Build-Out analysis can vary in complexity depending upon the complexity of the input GIS datasets, zoning requirements and the project funding. This project was burdened by the need for the development of a majority of the input GIS data layers, including tax parcel polygon coverage and soil based non-buildable areas. This project also had to make use of the best available map sources. Specifically, this includes the soil derived data layers of steep slopes and wetland areas. These datasets are 31

33 mapped at a less accurate scale and a more generalized manner than the Town Tax map, which makes them somewhat incompatible. Assumptions had to be made with modeling zoning requirements. Since we do not know the locations of the potential buildings, nor do we know the specific design of any subdivision, certain zoning requirements could not be addressed within the scope of this project. Frontage, building setbacks, and varied overlay district requirements are too site specific for this study. Therefore, Town Planner supplied adjustment factors were used to adjust the number of lots and units per existing lot at build-out. The central product of the Build-Out Analysis is the Build-Out Excel Workbook. This product can be edited by the Town to improve the accuracy of the Build-Out. It may similarly be edited to reflect actual development, as it happens over time. Editing the numbers for a single lot will automatically update the summary tables provided on the RESULTS sheet within the Workbook. 32