FLOOD04031

• County: Statewide
• Community: State of Colorado
• Stream Name: All
• Basin: Statewide
• Title: Subdivision Design in Flood Hazard Areas
• Date: 9/1/1997
• Prepared For: State of Colorado
• Prepared By: FEMA
• Floodplain - Doc Type: Educational/Technical/Reference Information

In Bucks County, the amount of development
aIlmved on any site is limited by the site's specific mix
of naturaf features. (See Figure 3-7.) ;\/0 filling or
encroachment is permitted on Hoodplains or alluvial
soils, or in streams, lakes, ponds, or wetlands.
Historically, the county has had serious flooding
problems. In light of this, county planners necessarily
emphasize maintaining natural drainage systems in
new developments. Further, only about 20 percent of
the villages in the county are served by public se\vers.
The remaining properties are serviced by on-site
wastewater disposal systems which, "vhen faulty, can
pose serious risks to ground\vater quality. And due to
the relatively high-density development that exists in
the villages, on-site disposal can be compromised when
the distance behveen absorption areas is not sufflcient
to permit adequate treatment or dilution of pollutants.
In addition to the flood plains, parts of the county are
broad, flat natural retention areas that do not drain \veIl
because of soil conditions and topography. The county
requires that 90 percent of every subdivision site in a
natural retention area be kept as open space.
Limits are also set for development in other sensitive
areas. On the basis of environmental standards, each
site where development is proposed is evaluated, and a
portion of it is designated as undevelopable.

Transferable Development Rights (TORs)
TOR systems are used to shift development from lands
and properties determined to be in need of protection
to\vard more desirable locations within a jurisdiction.
TDRs have been used to protect farmland, to prevent
demolition of historic buildings, to increase development
densities in targeted areas, and to protect environmen-
tally sensitive lands, including floodplains. A TOR
program takes some of the bundle of development rights
from one piece of property (the sending site) and
transfers or relocates it to another piece of property (the
receiving site). Sending sites may be defined categori-
cally (e.g., every farmland parcel over a certain acreage
and each parcel containing high-quality wetlands) or
geographically (every parcel vvithin a designated
district). Receiving areas may be determined on a case-
by-case basis or a receiving zone or district may be
established. (See the Amicus Curiae Brief of the National
Trust for Historic Preservation et al. in support of the
Tahoe Regional Planning Agency in SllitunJ v. TRP A).
TOR programs have been applied in more than 40
jurisdictions in 13 states in the last 20 years. Lee and
Collier Counties, Florida, and in the Pine Barrens
regions of New Jersey and Long Island, :\Jew York, have
used TDRs to protect environmentally sensitive lands,
particularly coastal wetlands and floodplains and
mangrove svvamps. Lee County is using its TOR
program to redirect development from some poorly
sited (and still undeveloped) subdivisions in coastal
wetlands.
TOI{ systems have been difficult to administer in
some jurisdictions because they require a high level of
cooperation from neighboring property o\vners of the
receiving site (the place ,vhere the density is transferred
to). There also has to be a high level of demand for
development in both the sending and receiving site. In

some cases, programs have been put in place but have
not succeeded because developers were satisfied with
the limited development density that was allmved in
the sending area, and the additional allo\vable density
in the receiving area \vas not a big enough incentive to
result in the relocation of development from the
sending site.

Low-Density Zoning
Zoning that permits development densities of one to
five dwelling units per acre (generally referred to as
large-lot zoning) is one of the most often-used land-use

Figure 3-7. Bucks County, Pennsylvania,
Environmental Protection Standards

Type 01 Area

Percent 01
Oevelopment Allowed

Floodplain and alluvial soils
Lakes and ponds
Weflands. swamps. and bogs
Natural retention areas
Steep slopes: 25% or greater
Steep slopes: 15-25%
Steep Slopes: 8-15~/O
Forests
Ponds and lake shores
Agricultural areas

0%

o
o
10
15
30
40
20-40
20-30
5-40

tools to protect floodplains. Lm"r-density zoning in
floodplains and adjacent to rivers and streams can be
helpful in minimizing impervious surfaces and
reducing the number of buifdings at risk. The CRS
program offers credit to communities that create
minimum lot sizes of 1 to 10 acres or more per
dvvelling unit.
But overreliance on lm.v-density zoning can be
detrimental in the long run because it encourages
inefficient sprawling development patterns. Sprmvl
results in a greater overall amount of land area
devoted to urban uses (e.g., roads, buildings, parking
lots), \vhich can have greater negative environmental
impacts on floodplains than well-planned higher-
density development. Furthermore, zoning codes that
mandate large residential lots do not necessarily pay
proper attention to drainage and erosion control on
individual sites. Lmv-density zoning along
vvaterways also reduces opportunities for people to
use and enjoy the \vater in that it removes or limits
public access. To \.vork effectively, low-density
zoning should not be the primary land-use tool aimed
at reducing or minimizing flood damage; it should be
used in combination \vith other regulations, such as
site plan revic\-v, to help minimize the impact of the
development on the natural features of the site. APA
and FEMA encourage communities to look beyond
low-density zoning for other methods to protect
floodplains.

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