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How scarce is developable land? . an imperative for smart growth. by Pat Dunlavey, July 2008. What got me started…. “Depending on how you do the calculations we have already protected between 48.9% and 81% of town ” – an email opposing the proposed wetlands bylaw

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how scarce is developable land

How scarce is developable land?

an imperative for smart growth

by Pat Dunlavey, July 2008

what got me started
What got me started…
  • “Depending on how you do the calculations we have already protected between 48.9% and 81% of town” – an email opposing the proposed wetlands bylaw
  • “…restrictions on development, especially in Williamstown, limit the number of families and add pressure on the residential tax base.” – Mt Greylock Long Range Financial Planning Committee Report

Protected Land

Land that is (permanently) excluded from residential or commercial development for purposes of agriculture, conservation or recreation

Upland Conservation District

Protected Open Space

* Hopkins Forest and Clark Art are not actually protected, but we’re counting them anyway

what about space for people
What about “space for people?”
  • We have 1.7 acres of non-protected land per-capita.(1) We rank 135th out of 351 towns in this measure.(2)
  • If we omit WC students, we have 2.2 non-protected acres per-capita, ranking 116th in the state.
  • Clark Art and Hopkins Forest were counted as protected open space
  • 2000 census figures; protected open space data for other towns from MassGIS, 2008
what is a build out analysis
What is a Build Out Analysis?
  • Quantify the impacts of various constraints, individually and in combination, on potential for (expansive) growth in each zoning district
  • Forecast growth trends
  • Project build-out dates for various zoning districts
  • Identify zoning that does not match demands for growth (too little - or too much - capacity)
the parts of the umass boa
The Parts of the UMass BOA
  • “Net Usable Land Area” in various zoning districts (Total area – “unusable” areas)
  • Land area that is partially constrained
  • Calculation of number of units that could, in theory, be built (before each zone is “built-out”)
  • Forecast future build rates, and project build-out dates for each zone
  • Conclusions
46 of williamstown has slopes 20 13 915 acres out of 30 005 38 has slopes 24 11 456 acres
46% of Williamstown has slopes >= 20% (13,915 acres out of 30,005); 38% has slopes >= 24% (11,456 acres)

[Slope (Percent)]=tan(deg2rad(slope([DEM (Meters)],3)))*100

SELECT * FROM [Slope (Percent)] WHERE [Height (I)] >= 20

SELECT Count(*) * 0.006177634536679134 as Acres FROM [SelectedAreaImage]

WHERE [Selection (I)]


70.5-3 (zoning bylaw; development standards; environmental protection)

(4) Impervious coverage.

(a) Except in the Village Business District, which is exempt from this limitation, impervious coverage shall not exceed the following percentages of site area, where "impervious coverage" is the area covered by building roof area plus paved areas, "site area" is the smallest single rectangle enclosing the area within which ground vegetation is removed for excavation, grading, drives, lawns or gardens and average slope is measured prior to site preparation.

AverageSite Area Slope

8% or less








24% or more

Maximum Impervious Coverage











30% of this site area has impervious cover (roof, paved driveway).

Average slope in the site area as delimited here is 25%

With these numbers, according to our bylaw, this house and driveway

should not have been built!


But add a bit of lawn to the plan to increase regulated site area, dropping impervious cover to 20%, and average slope to 20%

(Note that impervious cover outside of the property is counted)

two problems with impervious cover bylaw
Two problems with impervious cover bylaw
  • Objective is unclear
    • Much latitude for gaming the regulation
    • Given enough available site area, you can build on almost any slope – favors large sites
  • Off-parcel impervious cover counts if it’s in the site area
    • Neighbor’s activity may limit the amount of impervious cover you can have on your land, and vice-versa.
    • Partial solution: regulated site area = site area intersected with parcel boundary
Calculated area is high by ~3,000 acres

Counting local slopes over 20% as unbuildable does not make sense

We have examples of developments approved with local slopes well over 24%.

A site area with 20% average slope may have up to 20% impervious cover, yet the UMass study says it is unbuildable.

The UMass study’s unbuildable slopes - problems with accuracy and rationale…


Area with slopes >= 20%

  • 5m resolution DEM
  • No filter
  • No inner-buffer
  • 13,915 acres

Area with slopes >= 24%

  • 5m resolution DEM
  • No filter
  • No inner-buffer
  • 11,456 acres

Area with slopes >= 24%

  • 5m resolution DEM
  • Median filtered (5x5; ten passes)
  • Inner-buffered 25 meters
  • 8,942 acres
other 100 constraint categories
Other 100% Constraint Categories
  • Roads
  • Developed Land
  • Protected Open Space
  • River Protection Act 100’ Buffer
  • 100 Year Floodplain
  • Surface Water, Wetlands, Wetlands Buffer
  • Upland Conservation District

Protected Open Space

Town-owned: 1,359 acres

Other owners: 8,197 acres

Unprotected Open Space

Hopkins Forest:

1,990 acres*

Clark Art Institute:

127 acres

* within Williamstown


Upland Conservation

Overlay District

11,589 acres


Hydro constraints…

Surface water: 361 acres

RPA 100’ Buffer: 991 acres

100 Year Floodplains

1,056 acres


All 100% Constraint Categories

20,846 acres

NULA = 9,159 acres, or 31%

nula dunlavey 2008 v2
NULA: Dunlavey 2008 (v2)

* Excluding town-owned

boa partial constraints in rr2
BOA: Partial constraints in RR2
  • Comments:
  • I don’t agree that “temporary open space” (Chapter 61 land) is a constraint – certainly not 90%.
  • Percent constraint values are not to be considered accurate or reliable.
  • “Area free of all constraints”: was it calculated by subtracting “remaining acres” from “sum of areas free to develop”?
  • “Sum of areas free to develop” is not demonstrated anywhere in the report – presumably it is total acres in zone minus 100% constraints in zone

Partial Constraints and Costs

Slopes >= 15%

17,531 acres

Water Resources Districts 1 & 2 (minus sewer buffer)

4,734 acres

Wellhead Protection District

1,177 acres

Stream buffers

9,284 acres

RPA 200’ buffer

1,767 acres


Constraints have a cost dimension

  • Cost Surface:
  • Slopes (proportional)
  • Water Resources Districts 1 & 2 (minus sewer buffer)
  • Wellhead Protection District
  • RPA 200’ buffer + Stream 100’ buffers

Subdivided Lots 1998-2004

New growth records from 1996 to 2007 with property class of 130 or 132 (new residential lot) joined to the parcels map of 2004


The cost surface model correlates with where new subdivision happened

(It doesn’t predict where overall new growth happens)

Average modeled cost on 22 new subdivided parcels compared with all other parcels in NULA

Modeled cost on parcels showing new growth compared to those without (in NULA)

t=1.51, df=286, p<0.2

t=3.58, df=22.78, p<0.002


25% of NULA has a modeled constraint cost under the observed average for the subdivided parcels

Brightest Red = parcels whose modeled development cost is less than the 10 year average of actual subdivided parcels


Chapter 61 Land (2007)

7,060 acres

Ch61 Acres within NULA: 3,384 (37%)

Subtracting Ch61 from NULA…


Lowest Hanging Fruit:

Parcels <=1.155 in modeled constraint cost, minus Chapter 61 land

  • Bright red = less than 1.155 modeled cost
  • Shades of pink = less than 1.7 modeled cost (one standard deviation)
mount greylock long range financial planning committee final report says
Mount Greylock Long Range Financial Planning Committee Final Report says:

“As there is no such thing as a free lunch, there is no such thing as free open space. It comes at a cost—that of forgone income. …

As Mt. Greylock needs to face squarely the tradeoffs in its budget, so does the community need to face more squarely than it has the tradeoff between open space and the quality of municipal services, including education. If we as citizens want open space, as a majority in Williamstown clearly seem to, we must be willing to increase revenue by other means.”

chapter 61 land open space
Chapter 61 Land = Open Space
  • Most of the value that has recently been taken out of the tax base is through Chapter 61 tax shelters for working land, not permanently protected Open Space
  • It is not a community decision to shelter working land from taxation
  • It is not community policy to provide these tax shelters
  • Chapter 61 land is private land in every sense of the word – it is not open space
what is chapter 61 about
What is Chapter 61 about?
  • We reward people for not developing their working land
    • Neutralizes financial pressure to convert agriculture, forestry and recreation lands to residential use
    • But, tax burden is shifted to other property owners
  • Does not foreshadow intention of property owner with respect to future development
    • If you really wanted to save taxes and had no intention to ever “sell out” you would be better off to set up a permanent CR or APR
    • But Ch61 can be considered a cost factor against selling for development (you have to pay up to 5 years back taxes if you pull out)
a little reality check
A little reality check…
  • What zoning and other constraints allow does not mean it will happen quickly, or even at all!
  • Build Out Dates from UMass study:
    • RR2: 2175
    • GR1: 2089
    • GR2: 2348
why so slow
Why so slow?
  • If constraints and costs were inhibiting growth in the face of real demand, shouldn’t we expect to see the lowest hanging fruit go more quickly? (There’s a lot of low-hanging fruit out there.)
  • But the difference in subdivision rates, correlated to the cost surface, does suggest some degree of market sensitivity to costs/constraints, which should reduce the rate of new development.

Dumb answer: It’s probably a combination.

what is this growth imperative
What is this “growth imperative?”
  • Levies (to fund town, schools) need to increase ~$500K/year to maintain services, or about 4.5%
  • Proposition 2½ restricts increasing tax revenues from the existing tax base to 2.5% annually - new growth exempted
  • To the extent that we can cover this shortfall with new growth, we’re happy
  • ~$17M in annual new growth can cover the average budget shortfall

Result: a certain rate of new growth becomes a political imperative

new growth increases in property value due to actions of the owner
New growth = increases in property value due to actions of the owner
  • Improvements to existing buildings (decks, pools, remodeling, finish attic or basement, tear-down and rebuild, etc)
  • Subdividing land
  • New construction
two kinds of residential growth
Expanding out:

Build on unbuilt parcels

Subdivide and build on open land

Mature growth – in the existing footprint:

Improvements (same density)

Infill (increase density)

Two kinds of residential growth
  • Low hanging fruit gets harder to reach
  • Higher environmental impact
  • Changes community to an “exurban” model
  • Sustainable over long term
  • Lower environmental impact
  • Maintains relationship between village and countryside
new growth free money
New growth = free money
  • Proposition 2½ assumes that new growth produces offsetting costs (which explains the exemption for new growth)
  • The growth imperative relies on growing in a way that doesn’t generate new costs
    • Expensive retirement and 2nd homes (on large lots) = ‘good’
    • Family-friendly growth = ‘bad’
  • Even if successful in short-term, relying on expansive growth is a questionable strategy for the long run
    • As low hanging fruit is depleted, costs inhibit further demand
    • Changes community character
new growth valuations 1998 to 2007
New growth valuations 1998 to 2007

Subdivisions averaged19% of annual new growth

Could we satisfy “the growth imperative” without expansive growth?