HomeMy WebLinkAboutItem V PLAN COMMISSION STAFF REPORT FEBRUARY 19,2019
ITEM V: PUBLIC HEARING: PROPOSED ZONING ORDINANCE AMENDMENT TO
SECTION 30-156-FLOODPLAIN OVERLAY ZONING DISTRICT TO ADOPT
REVISED FEMA FLOOD INSURANCE RATE MAPS AND REGULATORY
FLOODPLAIN AND FLOOD STORAGE DISTRICT MAPS WITHIN THE
SAWYER CREEK WATERSHED
GENERAL INFORMATION
Applicant: Department of Community Development
Actions Requested:
The City of Oshkosh Department of Community Development requests review and approval of
an amendment to Section 30-156 of the Floodplain Overlay Zoning District to adopt amended
FEMA Flood Insurance Rate Maps as the regulatory zoning floodplain maps as well as the Flood
Storage District Maps.
Applicable Ordinance Provisions:
The Zoning Ordinance,Section 30-380, establishes the ability of the Common Council, on its own
motion or on petition after first submitting the proposal to the City Plan Commission, to amend,
supplement or change Zoning District boundaries or regulations of the Zoning Ordinance.
BACKGROUND INFORMATION
The City Department of Community Development requests review and approval of amended
floodplain overlay maps to reflect the proposed new Flood Insurance Rate Maps (FIRMs) that are
scheduled to become effective on March 271h1 2019. The proposed FIRM is based on a Flood
Insurance Study(FIS)for the Sawyer Creek Watershed dated 12/13/17. The new mapping is the
result of an extensive study undertaken by the City and its engineering consultant, Strand
Associates while working with the Federal Emergency Management Agency(FEMA) and
Wisconsin Department of Natural Resources (WDNR). Included in this mapping action are the
recently created Flood Storage Districts.
For clarification purposes, the FIRM maps address the floodplain issues related to insurance,
while the regulatory map addresses the development/regulatory issues. The FIRM boundaries
are adopted locally as a regulatory zoning overlay that generally includes the 100 year Floodplain
and Floodway. Also included for the first time are the recently created Flood Storage Districts.
The City of Oshkosh participates in the National Flood Insurance Program by adopting maps and
regulations pertaining to special flood hazard areas (the floodplain) that are commonly known as
the Flood Insurance Rate Map (FIRM). Only the Federal Emergency Management Agency
(FEMA) can amend the FIRMs and these maps are periodically updated to reflect modifications in
Page 1
the floodplain,which can also be initiated by property owners through the Letter of Map
Amendment(LOMA) or Letter of Map Revision (LOMR). If the City did not adopt the WDNR
Model Floodplain Ordinance,property owners within the FIRM would not be eligible to receive
flood insurance. Being mapped as a floodplain property, especially 100 year floodplain or
floodway, can significantly impact the developability of a property and/or be costly in terms of
having to obtain flood insurance.
On March 23,2003,the current city-wide Flood Insurance Rate Maps (FIRM)became effective
from a regulatory standpoint. This adoption action was required for the City to continue to
participate in the National Flood Insurance Program(NFIP). Shortly thereafter,the WDNR
completed a detailed analysis of Winnebago County,including the City of Oshkosh, developing a
digital floodplain from the 2-foot contour elevations, spot elevations, cross section analysis data,
and previous flood data. City staff has used this map from a regulatory standpoint since that
time, since it represents the most accurate available floodplain data.
Since the early 2000s,the City of Oshkosh has been working on improvements within the Sawyer
Creek Watershed to help alleviate regional flooding. Improvements such as construction of a
regional storm water detention basin at James Road, the dredging of Sawyer Creek and upgraded
bridges (Sawyer Street,Westfield Street and Witzel Avenue(County)) to increase cross sectional
area to allow more storm water to pass through the bridges have all improved drainage capacity.
These improvements as well as more refined field data collection have affected the regional
floodplain and in particular,the amount of land area and number of parcels that are mapped as
impacted by floodplain.
In order for the amended floodplain boundaries to take effect,the Common Council in late 2018
adopted a new floodplain district identified as a Flood Storage District(FSD). The FSDs are areas
mapped within the City and Winnebago County. The Winnebago County Board is scheduled to
consider the creation of the FSDs in early March of 2019.
On February 7,2019, the City and County held a joint public meeting on the proposed new maps
at the Coughlin Center. For notification purposes, the City mailed approximately 450 meeting
notices to all property owners impacted by the new mapping and included a link to information
on the City's website where all information and maps relative to the proposal are currently
located. The City's website also includes an interactive map that shows before and after
floodplain boundaries. Floodplain information can be found at:
https://www.ci.oshkosh.wi.us/PlanningServices/FloodPlainUpdate20l9.aspx
In order for the new floodplain maps to become effective,Winnebago County must map the flood
storage districts proposed outside of the City's jurisdiction in the Towns of Nekimi and Utica.
The Winnebago County Zoning Department is coordinating this process and the mapping will
need approval by the County Board.
Item V—Adopt new FIRMS,FIS&Flood Storage District Mapping 2
Page 2
ANALYSIS
The results of the City's efforts the past 15+years have modified the reginal floodplain elevation
within the Sawyer Creek Watershed. Through computer modeling and enhanced data collection,
the mapped floodplain and floodway have changed on over 400 properties within the City.
While the vast majority of properties will see no change to their current status with FEMA's
insurance requirements,60 properties are now shown to have no impact by the 100 year
floodplain or floodway. Conversely, 23 properties are now shown to be mapped with a portion
of 100 year floodplain or floodway on the property. This is mainly due to more refined data
gathering versus methods used on the current FIRMs. This does not necessarily mean the
property owners will be required to obtain flood insurance.
The proposed FIRMs take into account the creation of Flood Storage Districts. A Flood Storage
District is currently defined in 30-156 (C)(32) as "those floodplain areas where storage of
floodwaters has been taken into account during analysis in reducing the regional flood
discharge." A Flood Storage District(FSD) is a mapped area where flood storage capacity will be
protected where no increase in the amount of volume can be added in the FSD that would change
the height of the regional flood elevation. Basically,if a pail of dirt is added in an FSD, a pail of
dirt from another area of the property would need to be taken out to make up for the volume that
was added. The flood storage areas are calculated using computer models and actual ground
elevations.
The impact of the FSD is that development cannot be done that would cause an increase in the
regional flood elevation by removing flood storage volume. For development to occur,
"compensatory storage" would have to be provided. If compensatory storage cannot be
provided,the whole area has to be rezoned as a flood fringe district, which requires engineering
studies. This may mean providing engineering studies for even a simple development. The areas
that are being proposed as FSDs are areas that already"wet" and detain storm water during a
regional flood event but do so in an unofficial status. The majority of FSDs to be mapped in the
city generally involve existing detention basins so there should not be much of a practical impact
on development. The FSDs in the town areas generally involve lands used for agricultural
purposes and as previously stated do currently retain flood waters during a regional event. FSD
areas in the towns currently used agriculturally may continue to be farmed as long the ground
surface elevations are unaltered.
Adoption of the new FIRM's and FIS is the final step in completing the process to adopt new
Federal Emergency Management Agency Floodplain Maps,ensuring the City's continued
participation in the National Flood Insurance Program.
RECOMMENDATION
Staff recommends approval of the proposed Flood Insurance Rate Maps(FIRM),Flood Insurance
Study (FIS) and Flood Stargae District Mapping as proposed.
Item V—Adopt new FIRMs,FIS&Flood Storage District Mapping 3
Page 3
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