Tompkins County is dominated by significant water
bodies (lakes, ponds, rivers, and streams) that are critical to public health
and the economic and environmental well being of this area. Economic and
environmental activities dependent on the integrity of local water bodies and
water supplies include tourism, agriculture, industry, recreation, education
and research, and real estate. Although
wetlands are important components of environmental and economic systems,
federal and state agencies consider wetlands to be distinct from water bodies
for regulatory purposes.
Although water bodies and water supplies are
abundant in Tompkins County, certain activities can adversely affect the
ecological balance within water bodies, impairing their current and potential
economic and environmental functions.
Threats to local water supplies include both point source pollution
(often thought of as a single pipe draining a water body) and nonpoint source
pollution (which is broader in nature and originate from construction,
agriculture, parking lot and street runoff, stormwater runoff, on-site
wastewater systems, and commercial and residential activities).
How are Water
Bodies Regulated?
Federal and state agencies, such as the New York
State Department of Environmental Conservation (DEC) and United States Army
Corps of Engineers (Army Corps), require permits for activities that might
affect or disturb a water body and/or its banks. The stringency of these
permits corresponds with the DEC classification assigned to the water body (see
below) and may range from a general, or unified, permit to a permit tailored to
the specific site and type of work conducted.
Regulated activities might include streambank maintenance, construction,
flood protection and mitigation, dredging, placing fill, and certain agricultural
practices.
Commercial, industrial, and agricultural activities
that discharge to a water body require a State Pollution Discharge Elimination
System (SPDES) permit. This permit is
required for a broad range of activities, including the discharge of
wastewater, stormwater, or chemical and thermal emissions from municipal
treatment plants, industrial plants, utilities, large subdivisions, apartment
complexes, and confined animal feeding operations.
Prior to conducting stream-related work or discharging
wastewater, the Region 7 Office of the DEC or the Army Corps Buffalo District
should be contacted to obtain the necessary approvals and permits. Each of these agencies will automatically
forward permit applications to the other, and each agency will contact the
applicant if additional permits and/or paperwork are needed.
How are Water
Bodies Classified?
The DEC has assigned most water bodies within the
state a letter based on their existing or expected “best use.” The most
pristine waters are assigned a classification of AA; while the most degraded
waters are assigned a classification of D.
Class
|
Best Use |
|
AA |
Drinking (after
chlorination) |
|
A |
Drinking (after chlorination and
filtration) |
|
B |
Bathing |
|
C (T) |
Fishing (trout) |
|
C |
Fishing |
|
D |
Secondary contact recreation |
|
Source: New York State Department of Environmental
Conservation |
|
Additional classifications of “T” or “TS” can be
added if a water body has sufficient amounts of dissolved oxygen to support
trout and trout spawning. Water bodies that are designated as “C (T)” or higher
(i.e.,
“C (TS)”, “B”, or “A”) are collectively referred to
as "protected streams," and are subject to additional regulations.
Periodically, the DEC publishes the Priority
Waterbodies List (PWL), which includes a list of water bodies that do not meet
their designated “best use” classification.
A data sheet that describes the conditions, causes, and sources of water
quality degradation for each of the respective listings is also included in the
PWL. The PWL is used by the DEC and
other agencies as a primary resource for water resources management and
funding.
Many of the water bodies of Tompkins County
(streams, lakes, and ponds) are designated as protected streams due to their
importance as drinking water supplies or fish habitat. See the following map for the location of
protected streams in Tompkins County.
Fish
resources are a key factor in determining water body classifications because
they are the top of the food chain in aquatic habitats. As such, fish can be used as an indicator of
the overall quality of an aquatic ecosystem.
They are highly vulnerable, both directly and indirectly, to changes in
their environment. They can be directly
affected by physical and chemical changes in the water, and indirectly affected
when changes in the environment affect their food sources or the temperature
and turbidity of their habitat.
Cayuga
Lake includes two interrelated assemblages of species, one in the shallow
(littoral) zone and the second in the deep-water zone. In Tompkins County, the shallow zone is
limited to the southern lake basin and a narrow fringe along the lake margins
where light reaches the bottom.
The
shallow zone is home to a warm water fish community dominated by Smallmouth
Bass. Other important predator fish in
the shallow-water community include Largemouth Bass and Northern Pike. These species prey on Yellow Perch,
Pumpkinseeds, Bluegills, Rock Bass, and Minnows. Southern Cayuga Lake also supports a spawning population of White
Suckers.
Lake
Trout, Rainbow Trout, Brown Trout, and Landlocked Salmon are the dominant
predators in the deep-water community.
Of these salmonids, only the Lake Trout is native to Cayuga Lake. Populations of the Brown and Rainbow Trout,
Landlocked Salmon, and Lake Sturgeon are maintained (or, in the case of Rainbow
Trout, supplemented) by stocking. Juvenile salmonids prey on zooplankton. The quantity of zooplankton is considered to
be the limiting factor for the growth and survival of Cayuga Lake’s most
important sport fish, stocked juvenile lake trout. The Alewife is the predominant forage species. Other prey species include Rainbow Smelt,
Troutperch, and Slimy Sculpin.
The New York State Department of Environmental Conservation
(DEC) has designated several creeks in Tompkins County as protected partially
for the purposes of fish habitat. The
DEC stocks these creeks with various species of fish. Buttermilk Creek, Enfield Creek, Fall Creek, Salmon Creek, Six
Mile Creek, and Virgil Creek are stocked with Brown Trout. Rainbow Trout are stocked in Salmon Creek,
and Landlocked Salmon are stocked in Owasco Inlet.
Information about protected streams in Tompkins
County was copied from the DEC Region 7 Protected Stream maps. For a map of this information, in paper or
digital format, contact the Tompkins County Planning Department.
The
PWL and maps of protected streams can also be viewed at the Tompkins County
Soil and Water Conservation District.
For information about permitting, contact the Region 7 DEC Office or the
Army Corps of Engineers. Additional
information about the PWL can be obtained from the New York State Department of
Environmental Conservation (DEC)’s Division of Water.
Army Corps of Engineers,
Buffalo District (Attention: Regulatory Branch), 1776 Niagara St., Buffalo, NY,
14207-3199, 716‑879‑4330.
New
York State Department of Environmental Conservation, Div. of Water, 625
Broadway, Albany, NY 12233, 518‑402‑8233: http://www.dec.state.ny.us/website/regs/ch10.htm
http://www.dec.state.ny.us/website/dcs/streamprotection/index.html
New York State Department of
Environmental Conservation, Region 7 Office, 615 Erie Blvd. West, Syracuse, NY
13204-2400, 315-426-7403.
Tompkins County Planning
Department, 121 East Court Street, Ithaca, NY 14850, 607‑274‑5560.
Tompkins
County GIS Program, Information Technical Services, 128 East Buffalo Street,
Ithaca, NY 14850, 607-274-5418.
http://www.tompkins-co.org/gis
Tompkins County Soil and Water Conservation
District, 903 Hanshaw Rd, Ithaca, NY 14850, 607‑257‑2340.
What is a Watershed?
A
watershed is the land area that contributes water to a given point, such as a
stream or lake. Contributing sources of
water for a watershed include (but are not limited to) springs, streams, seeps,
ditches, culverts, marshes, wetlands, swamps, and ponds. Eventually, all surface water, some
groundwater resources, and precipitation falling within a watershed, drain into
a single receiving water body such as a stream, river, lake, or wetland. A watershed boundary is usually delineated
by connecting the highest elevation points in the area.
Watersheds
exist at various scales within a hierarchical structure. Gullies and ravines trickle into streams,
which in turn feed into larger streams or rivers. Each of these water bodies (gully, ravine, stream, etc.) drains
its own particular watershed so that larger watersheds are comprised of several
smaller watersheds. For example, the
Virgil Creek watershed flows into the Fall Creek watershed, which is contained
within the larger Cayuga Lake watershed.
While the term watershed is often used interchangeably with “drainage
basin”, the term drainage basin usually refers to a larger watershed such as
the Susquehanna River Drainage Basin or the Lake Ontario Drainage Basin.
Land
use throughout a watershed (or the commercial, industrial, agricultural, and/or
residential activities a land area can support) and the availability of
reliable water sources within a watershed are directly related. That is, the land use in a particular area
is often determined by the availability of reliable water supplies; and the
single most important determinant of the quality, quantity, and availability of
local water resources is land use.
Because of this dynamic relationship between water and land use, the
characteristics of the entire watershed must be considered when addressing
water quality and water quantity issues, including such factors as the amount
of impervious surface and effectiveness of local land management
practices. Additionally, the critical
influence and impact of water on important ecological and economic systems
(such as provision of drinking water, flooding, recreation, and future economic
growth) make watersheds increasingly popular and important management and
planning units.
Although
there are no regulations associated with a watershed, state and federal
agencies look favorably on water-related management and planning processes that
utilize the principles and concepts of watershed management.
The
land area within Tompkins County drains into two major river drainage basins:
the Oswego River basin, which drains north to Lake Ontario, and the Susquehanna
River basin, which drains south to the Chesapeake Bay. Over 383 square miles (245,545 acres) of
Tompkins County drain into the Oswego River basin directly or via Cayuga
Lake. Over 96 square miles (61,459
acres) of Tompkins County drain into the Susquehanna River. Tompkins County is a major contributor to
the Cayuga Lake water system, as the County comprises over half of the total
land area in the Cayuga Lake watershed.
Table 2: Watersheds in Tompkins County
Watershed
(Common Name)
|
Acres
|
Sq. Miles (approx.)
|
Drainage Basin
|
Cascadilla
Creek
|
8,664 |
13.54 |
Oswego |
Catatonk
Creek
|
25,266 |
39.49 |
Susquehanna |
Cayuga
Inlet
|
58,738 |
91.81 |
Oswego |
Cayuta
Creek
|
19,303 |
30.17 |
Susquehanna |
East
Cayuga Lakeshore North
|
9,217 |
14.41 |
Oswego |
East
Cayuga Lakeshore South
|
13,095 |
20.47 |
Oswego |
Fall
Creek
|
48,202 |
75.34 |
Oswego |
Owasco
Inlet
|
21,793 |
34.06 |
Oswego |
Salmon
Creek
|
21,817 |
34.10 |
Oswego |
|
Six
Mile Creek |
33,403 |
52.21 |
Oswego |
Taughannock
Creek
|
14,289 |
22.33 |
Oswego |
West
Branch Owego Creek
|
16,890 |
26.40 |
Susquehanna |
West
Cayuga Lakeshore North
|
2,794 |
4.37 |
Oswego |
|
West
Cayuga Lakeshore South |
13,533 |
21.15 |
Oswego |
|
TOTAL |
307,004 |
479.85 |
|
|
Source:
Tompkins County Planning Department |
|||
The following
map, developed at a scale of 1:200,000, illustrates 14 watersheds in Tompkins
County. Watershed boundary data and
areas are available in both paper and digital format from the Tompkins County
Planning Department.
Cayuga
Lake Watershed Intermunicipal Organization: http://www.cayugawatershed.org
Cayuga
Lake Watershed Network, P.O. Box 303, 8404 Main St., Interlaken, NY 14847, 607‑532‑4104.
Dutchess
County Department of Planning and the Dutchess County Environmental Management
Council. 1985.
Natural Resources. Dutchess County, NY: Dutchess County Cooperative Extension
Association.
EPA,
Surf your Watershed: http://www.epa.gov/surf/
EPA
Watershed Homepage: http://www.epa.gov/OWOW/watershed/
NRCS,
Hydrologic Unit Boundary Data: http://www.ftw.nrcs.usda.gov/huc_data.html
Tompkins
County GIS Program, Information Technical Services, 128 East Buffalo Street,
Ithaca, NY 14850, 607-274-5418.
http://www.tompkins-co.org/gis
Tompkins County Planning
Department, 121 East Court Street, Ithaca, NY 14850, 607‑274‑5560.
What is an Aquifer?
Aquifers are
geologic formations beneath the Earth’s surface that store and yield usable
amounts of groundwater. One or more
aquifers can lie beneath any given point on the Earth’s surface; and the
location, size, capacity, depth, and flow characteristics of an aquifer are
directly related to the geology and hydrology of the particular aquifer and its
recharge area. (See definition of
recharge area below.)
Aquifers are
usually described as confined or unconfined.
Typically, confined aquifers are covered with, or consist of, less
permeable substances such as clay or contiguous shale. Unconfined aquifers consist of unconsolidated
materials such as sand and gravel, which allow substances to easily percolate
from the surface to the aquifers below.
The uppermost
boundary of surficial aquifers (those closest to the Earth’s surface) is
defined by the water table, which is where the spaces in unconsolidated
sediments and the openings in bedrock are fully saturated. The spaces between soil and rock particles
in the unsaturated zone, located above the water table, are only partially
occupied by water. The water table
rises and falls depending on the rates of groundwater recharge and discharge
and the capacity of the aquifer.
Aquifers
can be replenished – or recharged – by the infiltration of precipitation and
surface water runoff through soil, as well as by the intermixing of surface
water resources such as streams and creeks.
The land area that contributes to this infiltration is called a recharge
area. Recharge areas may replenish
aquifers directly beneath them (as in the case of unconfined or surficial
aquifers) or they may recharge aquifers far away (as in the case of confined
aquifers).
Why are Aquifers Important?
Aquifers are
an important source of water for residential, commercial, and industrial
uses. Almost half of all Tompkins
County residents rely on groundwater to supply their drinking water needs. Additionally, in central New York,
groundwater typically contributes more than half of the total annual flow to
local streams and creeks.
Because
aquifers are replenished by the infiltration of surface water, impervious
surfaces (pavement from roads or parking lots, roofs, building footprints,
etc.) decrease recharge areas and threaten aquifers by inhibiting infiltration
of precipitation and surface water through the soil. Any contaminant contained in or near an aquifer, and/or its
recharge area may potentially contaminate the aquifer. Potential contaminants include bacteria and
pathogens leaching from septic systems; gas, salt and oil washed from parking
lots; fertilizers; pesticides; hazardous or toxic waste spills; and petroleum
or oil leaking from underground storage tanks.
Unlike
surface water, which flushes contaminants downstream relatively quickly,
groundwater in aquifers migrates relatively slowly and can take several years
or decades to move from the point of origin to the point of discharge. Once degraded, an aquifer can become
unusable, and oftentimes remediation is not technologically or economically
feasible. Moreover, because of
groundwater and surface water interactions, contamination in an aquifer may
eventually contaminate surface water as well.
The quantity
of water contained within an aquifer, and the aquifer’s ability to serve as a
reliable supply of water, must also be considered. Generally, an aquifer’s geology, retention, and recharge
characteristics determine the quantity of water available. When water is withdrawn at a rate faster
than it is recharged, the aquifer can be depleted. Generally, this occurs when too many wells withdraw water from an
aquifer.
Aquifers in Tompkins County
The
process of glaciation and the subsequent deposition of coarse sand and gravel
deposits heavily influenced the location, size, and capacity of aquifers in
Tompkins County. As a result, several
small discontinuous local aquifers in Tompkins County were created that support
limited numbers of wells while others supply vast quantities of water. The main aquifers in Tompkins County are
located in the major valleys that are comprised of sand and gravel, such as the
Cayuga Inlet valley, upper portions of the Six Mile Creek valley, and portions
of the Fall Creek valley. Bedrock
aquifers (interlayered sandstones, siltstones, and limestones) typically yield
much less water than sand and gravel aquifers.
Although bedrock aquifers may be sufficient to supply individual
residential units and small farms, the water may be heavily mineralized and
relatively unreliable.
The
following surficial aquifer map, developed at a scale of 1:24,000, indicates
the general location of large unconsolidated aquifers in Tompkins County. This map is not intended to be used for
detailed site evaluations, as the determination of precise aquifer locations
and characteristics requires additional evaluation. To construct this map, the U.S. Geological Survey (USGS)
inventoried well data and well-boring logs to identify the extent, depth, and
material characteristics of the surficial aquifers in the County.
To
get a copy of a digital file or a paper map of the surficial aquifers in
Tompkins County, contact the Tompkins County Planning Department or the local
USGS Office.
Miller,
Todd S. Sand and Gravel Aquifers of
Schuyler County, New York. 1990. U.S. Department of Energy, USGS,
Water-Resources
Investig.Report 90-4073.
Tompkins
County Planning Department, 121 E. Court Street, Ithaca, NY 14850, 607‑274‑5560.
U.S.
Geological Survey (USGS), 30 Brown Road, Ithaca, New York 14850, 607‑266‑0217.
Winter,
T.C., J.W. Harvey, O.L. Franke and W.M. Malley. 1998. Ground Water and Surface
Water: A Single Resource.
USGS
Circular.
What is a Wetland?
Wetlands,
according to the United States Army Corps of Engineers (Army Corps), are “those
areas that are inundated or saturated by surface or ground water at a frequency
and duration sufficient to support, and that under normal circumstances do
support, a prevalence of vegetation typically adapted for life in saturated
soil conditions. Wetlands generally
include swamps, marshes, bogs, wet meadows, and similar areas.” According to the New York State Department
of Environmental Conservation (DEC), “Freshwater wetlands are those areas of
land and water that support a preponderance of characteristic wetlands plants
that out-compete upland plants because of the presence of wetlands hydrology
(such as prolonged flooding) or hydric (wet) soils. Freshwater wetlands commonly include marshes, swamps, bogs, and
fens.” Wetlands
such as swamps and marshes are often easily recognizable, but some wetlands,
such as forested wetlands and wet meadows, are not obvious because they are dry
during part of the year.
Why are Wetlands Important?
Wetlands
are a critical component of natural ecosystems and provide a variety of
benefits such as:
·
filtering
harmful toxins, nutrients, and sediment from surface and stormwater runoff;
·
storing
floodwaters and reducing the magnitude of flood events; and
·
providing
valuable habitat for a diverse array of flora and fauna, including many rare,
threatened, or endangered species.
The
recreational uses associated with wetlands are also very diverse and include
birdwatching, hunting, and fishing, all of which provide direct economic
benefits to local communities. Because
wetlands are crucially important both economically and environmentally, they
are highly regulated by the Army Corps and the DEC.
How are Wetlands
Regulated?
The
National Wetlands Inventory was developed by analyzing aerial photographs and
can be used to locate wetlands that are at least one acre in size, however,
locations of wetlands should be verified by the Army Corps.
Additionally, the Army Corps issues wetland permits for the
placement of fill or dredge materials and the construction of certain
structures in waterways (navigable and non-navigable) and wetlands. Disturbances to wetlands must be mitigated
in accordance with Army Corps regulations.
The Army Corps permit required for activities within a wetland, and the
amount of wetlands mitigation required, vary depending on the type of project
proposed and the area of wetland impacted.
The
DEC regulates wetlands that are 12.4 acres or larger in size (this is based on
the metric system: 12.4 acres = 5 hectares).
For any work occurring within a wetland or within 100 feet of a wetland
boundary, the DEC requires that a wetlands permit be obtained.
Prior to conducting work in or near a wetland, the
Region 7 Office of the DEC or the Army Corps Buffalo District should be
contacted to obtain the necessary approvals and permits. Each of these agencies will automatically
forward permit applications to the other, and each agency will contact the
applicant if additional permits and/or paperwork are needed. If permits are not obtained or wetlands are improperly
altered, the Army Corps and the DEC have the authority to levy fines.
How are Wetlands Classified?
The
DEC classifies wetlands according
to their respective functions, values, and benefits.
Of the four classes of wetlands, Class I wetlands are the most valuable
and are subject to the most stringent standards.
The Army Corps classifies
wetlands only according to their species composition.
Wetlands in Tompkins County
Tompkins
County contains both NYS DEC Freshwater Wetlands (as determined by the DEC) and
National Wetlands (as determined by the U.S. Fish and Wildlife Service) as
shown in the following tables:
|
Municipality |
Acres of NYS DEC Freshwater Wetlands |
Percent of Municipal Land |
Acres of National Wetlands |
Percent of Municipal Land |
|
City of Ithaca |
27.295 |
0.70 |
470.11 |
12.08 |
|
Town of Caroline |
554.890 |
1.57 |
1,020.92 |
2.90 |
|
Town of Danby |
935.900 |
2.71 |
1,186.73 |
3.44 |
|
Town of Dryden |
2,102.970 |
3.49 |
3,401.03 |
5.93 |
|
Town of Enfield |
162.347 |
0.69 |
694.56 |
2.94 |
|
Town of Groton |
728.168 |
2.30 |
1,486.83 |
4.79 |
|
Town of Ithaca |
75.948 |
0.39 |
1,129.57 |
5.83 |
|
Town of Lansing |
596.263 |
1.33 |
6,840.56 |
15.50 |
|
Town of Newfield |
230.466 |
0.61 |
526.68 |
1.39 |
|
Town of Ulysses |
75.267 |
0.32 |
3,046.19 |
13.01 |
|
Vil. of Cayuga Hgts |
0.000 |
0.00 |
62.66 |
5.59 |
|
Village of Dryden |
39.830 |
3.83 |
111.92 |
10.77 |
|
Village of Freeville |
43.850 |
6.28 |
22.98 |
3.29 |
|
Village of Groton |
39.420 |
3.70 |
101.03 |
9.49 |
|
Village of Lansing |
18.850 |
0.65 |
30.25 |
1.04 |
|
Vil. of Trumansburg |
0.000 |
0.00 |
0.05 |
0.00 |
|
Total Tompkins Co. |
5,631.464 |
1.75 |
19,803.18 |
6.78 |
|
Source: Tompkins County Planning Department, based on USFWS data |
||||
NOTE:
The NYS DEC Freshwater Wetlands and the National Wetlands Inventory data above
includes Cayuga Lake in the total number of municipal acres listed and is
factored into the calculation for “Percent of Municipal Land”.
Maps and Data
The
following NYS DEC Freshwater Wetlands and National Wetlands Inventory maps were
developed at a scale of 1:24,000 and indicate the general location of wetlands
in Tompkins County.
Although the Army Corps and the DEC create and periodically update
wetlands maps, these maps are developed for use at a scale of 1:200,000 and are
best used as an indicator that wetlands are present, and that an on-ground,
site-specific investigation by a qualified wetland specialist (Army Corps
Engineer or private consultant) is warranted.
Many wetlands do not appear on wetland maps, so if land appears to be
wet, or has typical wetland plants or soils, landowners should call the Army
Corps or the DEC prior to altering the land to avoid wetland destruction and possible
fines.
For digital and paper copies of federal and state wetlands,
contact the Tompkins County Planning Department or the U.S.
Army Corps of Engineers. For information about the origin of the wetlands data
(metadata), contact the Cornell University Geospatial Information Repository
(CUGIR).
For
questions about wetlands on active farmlands or the Wetlands Reserve Program
(which makes payment to landowners for establishing wetland easements on their
agricultural property), contact the USDA Natural Resources Conservation
Service, Ithaca Office.
Resources and References
Cornell University Geospatial Information Repository (CUGIR) http://cugir.mannlib.cornell.edu/
Mitsch, W.J. and J.G. Gosselink. 1986. Wetlands. New York: Van
Nostrand Reinhold
New
York State Department of Environmental Conservation
http://www.dec.state.ny.us/index.html
.
New
York State Department of Environmental Conservation, Region 7 Office, 615 Erie
Blvd. West, Syracuse, NY 13204-2400, 315-426-7403.
Tompkins
County Planning Department, 121 East Court Street, Ithaca, NY 14850, 607‑274‑5560.
U.S. Army Corps of Engineers: http://www.usace.army.mil/inet/functions/cw/cecwo/reg/techbio.htm
U.S. Army Corps of Engineers, Buffalo District, Regulatory Branch,
1776 Niagara Street, Buffalo, NY 14207, 716-879-4330
NYS Department of Environmental Conservation, Division of Environmental
Permits, P.O. Box 1285, Fisher Avenue, Cortland, NY 13045-1090, 607-753-3095
http://www.lrb.usace.army.mil
U.S. Fish and Wildlife Service, Division of Habitat Conservation,
National Wetlands Inventory: http://www.nwi.fws.gov/
USDA Natural Resources Conservation Service (NRCS), Ithaca Office,
903 Hanshaw Rd., Ithaca, NY 14850, 607-257-3820.
USDA / NRCS, Wetlands Reserve Program:
http://www.nrcs.usda.gov/programs/wrp/
and Wetland
Science Institute: http://www.pwrc.usgs.gov/WLI/
Flood
Hazard Areas (FHA) are areas that the Federal Emergency Management Association
(FEMA) has determined to be vulnerable to flooding (see table on next page for
a description of flood event frequencies).
Flood
events are part of natural hydrological and seasonal cycles. The size and location of the areas which are
typically inundated during flood events, as well as the magnitude of the event,
are significantly influenced by the total area of impervious surface (roads,
parking lots, etc.) and wetlands within a watershed. Creation of, or increases in, impervious surfaces, diversion of
water off the landscape (to ditches or nearby water bodies), and the loss of
wetlands which help store and control floodwaters also cause higher volumes and
peak flows of stormwater runoff. It
should also be noted that, while floods can cause damage to the infrastructure,
the economy, and the environment, periodic inundation can benefit the habitat
of certain flora and fauna species and add nutrients to agricultural lands
located in flood areas.
FEMA
produces paper Flood Insurance Rate Maps (FIRMs) to show areas subject to
flooding as determined by historic, meteorological, and hydrological data, as
well as open space conditions, flood control structures, and land use in the
watershed at the time the FEMA study is conducted. These maps delineate Special Flood Hazard Areas, commonly
referred to as 100-year or base flood areas.
These maps may also include the elevation of the base flood (100-year
flood event), flood insurance risk zones, and areas subject to inundation by a
500-year flood event, all of which may be used to establish the National Flood
Insurance Program’s (NFIP) flood insurance premiums.
FIRMs
exist for every municipality in Tompkins County, with two exceptions: the Town
of Enfield and the Village of Cayuga Heights.
(The Village of Cayuga Heights has been certified by FEMA as having no
SFHAs; and the Town of Enfield does not participate in NFIP.) In all other municipalities, 100-year flood
zones have been identified and mapped.
Additionally, base flood elevations are recorded for the Village of
Groton, the Village of Dryden, the Town of Ithaca, the City of Ithaca and along
Cayuga Lake in the Town of Lansing, the Village of Lansing, and the Town of
Ulysses. FIRMs may also identify
floodways, which are defined as water body channels plus any adjacent
floodplain areas that must be kept free of encroachments so that the 100-year flood
discharge can be conveyed without increasing the elevation of the 100-year
flood more than a specified amount.
Floodways are mapped in the City of Ithaca, the Village of Dryden, and
the Village of Groton.
FEMA
has created a digital version of the FIRMs, called Q3 Flood Data, to be used
for post-disaster response and recovery, as well as general planning
purposes. This digital data displays
500-year flood zones, 100-year flood zones, and areas outside these flood zones
for all such areas defined on the paper FIRMS.
Q3
Flood Data differs from the paper FIRMs in that the Q3 Flood Data does not
include base flood elevation information necessary for engineering analysis and
site design. FEMA also notes that Q3
Flood Data should not be used to identify the flood-prone status of a property
within 250 feet of a Special Flood Hazard Area, nor should it be used for site
design, engineering, or flood insurance policy rating for properties in a
Special Flood Hazard Area. All site
specific information should be taken from the paper FIRMs.
The
measurement used to estimate the frequency of a flood event can be confusing
because a 100-year flood event is not a flood event that is likely to occur
once every 100 years. Rather, it has a
one percent chance of occurring or being exceeded during a one-year period, a
10% of occurring during a 10-year period, an 18% chance of occurring in a
20-year period, and so on. The
following table shows the likelihood of occurrence of flood events during
specified intervals of time.
Table 4: Likelihood of
Experiencing at Least One Flood Event
|
Flood Event |
|
||||||
|
In 1 year |
In 10 years |
In 20 years |
In 25 years |
In 30 years |
In 50 years |
In 100 years |
|
|
10-year |
10% |
65% |
88% |
93% |
96% |
99% |
99.99% |
|
25-year |
4% |
34% |
56% |
64% |
71% |
87% |
98% |
|
50-year |
2% |
18% |
33% |
40% |
45% |
64% |
87% |
|
100-year |
1% |
10% |
18% |
22% |
26% |
39% |
63% |
|
500-year |
0.2% |
2% |
4% |
5% |
6% |
10% |
18% |
|
Source: Water Courses Vol. 5, Issue 1, Spring 1998. A Newsletter from Cornell Cooperative
Extension and the Department of Soil, Crop and Atmospheric Sciences, Cornell
University |
|||||||
Finally,
it is important to note that many FIRMs for Tompkins County are outdated
because development occurring in floodplains has altered flood hazard areas
over time. Until FEMA updates the maps,
planners and landowners should be aware that areas that will actually flood
might vary significantly from the mapped FHAs.
To
order official FIRMs or Q3 Flood Data, contact FEMA’s Map Service Center. You can also view the FIRM maps or get Q3
Flood Data area maps at the Tompkins County Planning Department.
FEMA’s
Map Service Center: http://www.fema.gov/maps.shtm
FEMA’s Map Service Center, P.O. Box 1038, Jessup,
MD 20794-1038, Tel: 800‑358‑9616, Fax: 800‑358‑9620. Information and an Adobe Acrobat order form
is available at http://www.fema.gov/help/index.shtm#pdf
FEMA’s
National Flood Insurance Program: http://www.fema.gov/nfip/
FEMA's Q3 Flood Data Users Guide is available at
http://www.fema.gov/fhm/fq_q3.shtm
Tompkins County Planning
Department, 121 East Court Street, Ithaca, NY 14850, 607‑274‑5560.