Stormwater Management Plan
Tulsa's floodplain and stormwater program includes three key
goals:
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Prevent new problems.
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Correct existing problems.
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Enhance the community's safety, environment, and quality of
life.
This page highlights major program elements used to achieve
those goals.
Regulation
In general, Tulsa growth is welcomed - so long as it will not
flood or cause flooding elsewhere.
Beyond the 100-year
standard
Experience showed that the National Flood Insurance Program's
minimum standard is insufficient for Tulsa. Therefore, the city's
regulations exceed NFIP's standard in several important ways,
highlighted below.
Ultimate watershed
urbanization. Runoff generally becomes deeper and faster, and
floods become more frequent, as watersheds develop. Water that once
lingered in hollows, meandered around oxbows, and soaked into the
ground now speeds downhill, shoots through pipes, and sheets off
rooftops and paving.
Insurance purposes
require the NFIP floodplain maps to be based on existing watershed
development.
But unless plans and regulations are
based on future watershed urbanization, development permitted today
may well flood tomorrow as uphill urbanization increases runoff.
Tulsa enforces the NFIP minimum regulations and maps, to retain
eligibility for federal flood insurance.
In addition, the city enforces its own
more extensive maps and regulations, which are based on ultimate
watershed urbanization as forecast in the comprehensive plan.
Watershed-wide regulation.
Floodplains are only part of flood-management considerations. Water
gathers and drains throughout entire watersheds, from uplands to
lowlands. Each watershed is an interactive element of the whole. A
change at one place can cause changes elsewhere, whether planned or
inadvertent.
Stormwater detention. One way
to avoid increased flooding downstream from new development is to
provide stormwater detention basins throughout watersheds.
New or substantially improved
developments must detain the excess stormwater on site - unless
they are exempted in master plans or allowed to pay a fee in lieu
of on-site detention. Water from detention basins is released
slowly downstream.
In-lieu fees are allocated for regional
detention facilities. In most instances, the city has found
regional detention basins to function more satisfactorily than
smaller, scattered on-site facilities.
Valley storage. Flood water
cannot be compressed. It requires space. Encroachments into a
channel or floodplain can dam, divert, or displace flood waters. So
Tulsa requires compensatory excavation if a development - including
a flood control project - would reduce valley storage. Preserving
or recreating floodplain valley storage is a keystone of the city's
program.
Freeboard. NFIP regulations
require finished floors of new development to be at or above the
base flood elevation, based on existing watershed conditions. Tulsa
includes freeboard as another margin of safety, requiring finished
floors to be at least 1 foot above the regulatory flood elevation,
based on ultimate watershed urbanization.
Erosion and sedimentation.
Erosion and sedimentation rob hillsides of valuable topsoil, dam
lowlands, clog streams, and pollute rivers. Builders must control
site erosion from new development.
Permits and performance
standards. Tulsa requires a watershed development permit to be
issued before developing, redeveloping, building, excavating,
grading, regrading, paving, landfilling, berming, or diking of any
property within the city. There are five types of watershed
development permits: floodway, floodplain, stormwater drainage,
stormwater connection, and earth change permits. Individual
residential lots outside the floodplain are exempted.
Tulsa's regulations are based on
adopted floodplain maps (both Tulsa and NFIP), watershed-wide
master drainage plans, and development permits based on specific
performance standards.
Tulsa's Stormwater Management
Plan, Page 2
