HomeMy WebLinkAbout36. 19-66 JANUARY 8, 2019 JANUARY 22, 2019 19-30 19-66 ORDINANCE
FIRST READING SECOND READING
(CARRIED 6-0 LOST LAID OVER WITHDRAWN )
PURPOSE: AMEND SECTION 30-156 FLOODPLAIN OVERLAY ZONING
DISTRICT OF CHAPTER 30 ZONING ORDINANCE TO CREATE
A FLOOD STORAGE DISTRICT
INITIATED BY: COMMUNITY DEVELOPMENT
PLAN COMMISSION RECOMMENDATION: Approved
AMENDMENT TO THE GENERAL ORDINANCE OF THE CITY OF OSHKOSH TO
AMEND SECTION 30-156 FLOODPLAIN OVERLAY ZONING DISTRICT TO CREATE
A FLOOD STORAGE DISTRICT
The Common Council of the City of Oshkosh do ordain as follows:
SECTION 1. That new Section 30-156(D)(3)(d)regarding establishment of districts
is hereby created to add: Flood Storage District (FSD) is that area of the floodplain where
storage of floodwaters is calculated to reduce the regional flood discharge.
SECTION 2. That new Section 30-156(I) regarding development standards for add
Flood Storage Districts is hereby created as follows:
(I) Flood Storage District
(1) General. The flood storage district delineates that portion of the
floodplain where storage of floodwaters has been taken into account
and is relied upon to reduce the regional flood discharge. The
district protects the flood storage areas and assures that any
development in the storage areas will not decrease the effective flood
storage capacity which would cause higher flood elevations.
(a) Applicability. The provisions of this division apply to all areas
within the Flood Storage District as shown on the official
floodplain zoning maps.
JANUARY 8, 2019 JANUARY 22, 2019 19-30 19-66 ORDINANCE
FIRST READING SECOND READING CONT'D
(b) Permitted Use. Any structure, land use or development is
allowed in the underlying zoning district if the standards in
Section 30-156(I)(1)(c) are met, the use is not prohibited by
this or any other Ordinance or regulation and all permits or
certificates specified in Section 30-156(x) have been issued.
(c) Standards for development in Flood Storage Districts
(i) Development in flood storage district shall not cause
an increase equal or greater than 0.00 of a foot in the
height of the regional flood.
(ii) No development shall be allowed which removes
flood storage volume unless an equal volume of
storage as defined by the pre-development ground
surface and the regional flood elevation shall be
provided in the immediate area of the proposed
development to compensate for the volume of storage
which is lost (compensatory storage).
(iii) If compensatory storage cannot be provided, the area
may not be developed unless the entire area zoned as
flood storage district- on this waterway- is rezoned to
the floodfringe district. This must include a revision to
the floodplain study and map done for the waterway
to revert to the higher regional flood discharge
calculated without floodplain storage, as per Section
30-156 (L) of this chapter.
(iv) No area may be removed from the flood storage
district unless it can be shown that the area has been
filled to the flood protection elevation and is
contiguous to other lands lying outside of the
floodplain.
SECTION 3. Existing subsections 30-156(I) thru (L), inclusive, are hereby
renumbered (J) thru (M) respectively and references to these subsections within Chapter
30 are hereby renumbered accordingly.
JANUARY 8, 2019 JANUARY 22, 2019 19-30 19-66 ORDINANCE
FIRST READING SECOND READING CONT'D
SECTION 4. Publication Notice. Please take notice that the City of Oshkosh
enacted Ordinance #19-66 AMEND SECTION 30-156 FLOODPLAIN OVERLAY
ZONING DISTRICT OF CHAPTER 30 ZONING ORDINANCE TO CREATE A FLOOD
STORAGE DISTRICT on January 22, 2019. This ordinance amends Chapter 30 Zoning
Ordinance to create a Flood Storage District and associated development standards. The
full text of the Ordinance may be obtained at the Office of the City Clerk, 215 Church
Avenue and on the City's website at www.ci.oshkosh.wi.us. Clerk's phone: (920) 236-
5011.
,eta'
City
of
Oshkosh
TO: Honorable Mayor and Members of the Common Council
FROM: Darryn Burich
Director of Planning Services
DATE: January 2, 2019
RE: Amend Chapter 30 Zoning Ordinance to Create Flood Storage District within
Section 30-156 of the Floodplain Overlay District (Plan Commission
Recommends Approval)
BACKGROUND
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). The FIRM maps can only be amended by the
Federal Emergency Management Agency (FEMA) and these maps are periodically updated to
reflect improvements done in the floodplain, which can also be initiated by property owners
through the Letter of Map Amendment (LOMA) or Letter of Map Revision (LOMR). Through
the Zoning Ordinance the City has adopted a Floodplain Overlay District that mirrors the FIRM
and acts as the local regulatory tool that regulates development in the floodplain. If the City did
not adopt the DNR 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.
For the past few years the City of Oshkosh has been working on improvements to the Sawyer
Creek floodplain to help alleviate regional flooding in that watershed. Improvements such as
creation of a regional stormwater detention basin at James Road, the dredging of Sawyer Creek
and improvements to various bridges (Sawyer Street, Westfield Street and Witzel Avenue
(County)) to add cross sectional area to allow more stormwater to pass through the bridges have
all improved drainage capacity. These improvements will impact the regional floodplain and
in particular the amount of land area and parcels that are mapped as floodplain for which the
City will be requesting adoption of new Floodplain maps in 2019. In order for the "new"
floodplain boundaries to take effect, the City has to create a new floodplain district identified as
a Flood Storage District (FSD). Once created, both the City and Winnebago County must map
the Flood Storage District areas in order for the new FIRMs to take effect, which will be done as
part of one overall request in 2019.
City Hall,215 Church Avenue P.O.Box 1130 Oshkosh,WI 54903-1130 920.236.5000 http://www.ci.oshkosh.wi.us
ANALYSIS
A flood storage area 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 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. Currently, per 30-156 (D)(3) the regional floodplain is divided into three districts.
Staff is proposing to add a fourth district: (d) Flood Storage District (FSD) is that area of the
floodplain where storage of floodwaters is calculated to reduce the regional flood discharge.
Each of the districts has associated development standards and as such Section 30-156 (I)is being
amended to add Flood Storage District with the associated development standards. 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 per (ii) above. For development to occur,
"compensatory storage" per(iii) above must be provided. If it can't be provided, the whole area
has to be rezoned as a flood fringe district, which would require engineering studies. This may
mean providing engineering studies for simple developments. The areas that will be proposed
to be mapped as FSD's are areas that already "wet" and detain stormwater in an unofficial
status. Once the Zoning Ordinance is amended to include the Flood Storage Districts, staff will
start the mapping process with the County that will involve notification and public meetings.
Because of proposed placement of the FSD after standards for the General Floodplain District in
30-156 (I), it will displace all the subsections below it which will also be renumbered as part of
the amendment process.
FISCAL IMPACT
Flood Storage District areas are not being mapped at this time and this action only creates the
overlay district in the Zoning Ordinance. Once mapped there will be a resulting fiscal impact
due to any proposed development in an FSD area having to prove, through engineering studies,
that it is not increasing volume by removing flood storage capacity. Detailed studies are also
already required for development in the 100 year floodplain.
RECOMMENDATION
The Plan Commission recommended approval of zoning text amendments at its December 18,
2018 meeting.
Respectfully Submitted, Approved:
Darryn Burich Mark A. Rohloff
Director of Planning Services City Manager
City Hall,215 Church Avenue P.O.Box 1130 Oshkosh,WI 54903-1130 920.236.5000 http://www.ci.oshkosh.wi.us
ITEM: PUBLIC HEARING: PROPOSED ZONING ORDINANCE AMENDMENT TO
CREATE FLOOD STORAGE DISTRICT WITHIN SECTION 30-156 OF THE
FLOODPLAIN OVERLAY ZONING DISTRICT
Plan Commission meeting of December 18, 2018.
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 add Flood Storage
District(FSD) as part of the regional floodplain area.
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 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). The FIRM maps can only be amended by the Federal
Emergency Management Agency (FEMA) and these maps are periodically updated to reflect
improvements done in the floodplain,which can also be initiated by property owners through the
Letter of Map Amendment(LOMA) or Letter of Map Revision(LOMR). Through the Zoning
Ordinance the City has adopted a Floodplain Overlay District that mirrors the FIRM and acts as
the local regulatory tool that regulates actual development in the floodplain. If the City did not
adopt the DNR 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.
For the past few years the City of Oshkosh has been working on improvements to the Sawyer
Creek floodplain to help alleviate regional flooding in that watershed. Improvements such as
creation of a regional stormwater detention basin at James Road,the dredging of Sawyer Creek
and improvements to various bridges (Sawyer Street,Westfield Street and Witzel Avenue
(County)) to add cross sectional area to allow more stormwater to pass through the bridges have
all improved drainage capacity.These improvements will impact the regional floodplain and in
particular the amount of land area and parcels that are mapped as floodplain for which the City
will be requesting adoption of new Floodplain maps in 2019.
In order for the "new" floodplain boundaries to take effect, the City has to create a new
floodplain district identified as a Flood Storage District(FSD). Once created,both the City and
Winnebago County must map the Flood Storage District areas in order for the new FIRMS to take
effect,which will be done as part of one overall request in 2019.
ANALYSIS
A Flood Storage 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.
Currently,per 30-156 (D)(3) the regional floodplain is divided into three districts:
(a) The Floodway District(FW)
(b) The Floodfringe District(FF)
(c) The General Floodplain District(GFP)
Staff is proposing to add a fourth district:
(d) Flood Storage District(FSD) is that area of the floodplain where storage of floodwaters
is calculated to reduce the regional flood discharge.
Each of the districts has associated development standards and as such Section 30-156 (I) is being
amended to add Flood Storage District with the associated development standards. The specific
language proposed is:
(I) Flood Storage District
(1) General. The flood storage district delineates that portion of the
floodplain where storage of floodwaters has been taken into account and
is relied upon to reduce the regional flood discharge. The district protects
the flood storage areas and assures that any development in the storage
areas will not decrease the effective flood storage capacity which would
cause higher flood elevations.
(a) Applicability. The provisions of this division apply to all areas
within the Flood Storage District as shown on the official
floodplain zoning maps.
(b) Permitted Use. Any structure, land use or development is allowed
in the underlying zoning district if the standards in Section 30-
156(I)(1)(c) are met, the use is not prohibited by this or any other
Ordinance or regulation and all permits or certificates specified
in Section 30-156(K)have been issued.
Iter:-Text Air:endrn:ents Zoning Ordinance 2
(c) Standards for development in Flood Storage Districts
(i) Development in flood storage district shall not cause an
increase equal or greater than 0.00 of a foot in the height
of the regional flood.
(ii) No development shall be allowed which removes flood
storage volume unless an equal volume of storage as
defined by the pre-development ground surface and the
regional flood elevation shall be provided in the immediate
area of the proposed development to compensate for the
volume of storage which is lost(compensatory storage).
(iii) If compensatory storage cannot be provided, the area may
not be developed unless the entire area zoned as flood
storage district- on this waterway-is rezoned to the
floodfringe district. This must include a revision to the
floodplain study and map done for the waterway to revert
to the higher regional flood discharge calculated without
floodplain storage,as per Section 30-156 (L) of this
chapter.
(iv) No area may be removed from the flood storage district
unless it can be shown that the area has been filled to the
flood protection elevation and is contiguous to other lands
lying outside of the floodplain.
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 per(ii) above. For development to
occur, "compensatory storage" per (iii) above must be provided. If it can't be provided,the
whole area has to be rezoned as a flood fringe district, which would require engineering studies.
This may mean providing engineering studies for simple development. The areas that will be
proposed to be mapped as FSD's are areas that already"wet" and detain stormwater in an
unofficial status.
Included within this staff report is a map showing the potential locations for FSD's. The majority
of ones to be mapped in the city generally involve existing detention basins. The ones in the town
areas generally involved agricultural lands.
Attached to this staff report is also a FAQ regarding FSD's prepared by the Wisconsin DNR. The
FAQ does a good job in explaining what FSD's are and the impact of being in a FSD/
Once the Zoning Ordinance is amended to include the Flood Storage Districts, staff will start the
mapping process with the County that will involve notification and public meetings.
Because of proposed placement of the FSD after standards for the General Floodplain District,in
30-156 (1),it will displace all the subsections below it which will also be renumbered as part of the
amendment process.
Item-TextAntendn:ents-Zoniieg Ordinance 3
RECOMMENDATION
Staff recommends that the Plan Commission recommend approval of the proposed amendments
to add Flood Storage Districts and general renumbering to the Zoning Ordinance's Floodplain
District Overlay 30456 as proposed.
The Plan Commission approved of the proposed amendments to add Flood Storage Districts and
general renumbering to the Zoning Ordinance's Floodplain District Overlay 30-156 as requested.
The following is the Plan Commissions discussion on this item.
Mr. Burich discussed the amendments to the Zoning Ordinance as presented in the staff report.
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). The FIRM maps can only be amended by the Federal
Emergency Management Agency (FEMA) and these maps are periodically updated to reflect
improvements done in the floodplain. Through the Zoning Ordinance the City has adopted a
Floodplain Overlay District that mirrors the FIRM and acts as the local regulatory tool that
regulates actual development in the floodplain. If the City did not adopt the DNR Model
Floodplain Ordinance, property owners within the FIRM would not be eligible to receive flood
insurance. Being mapped as a floodplain property can significantly impact the developability of a
property and/or be costly in terms of having to obtain flood insurance. In order for the "new"
floodplain boundaries to take effect, the City has to create a new floodplain district identified as a
Flood Storage District (FSD). Once created, both the City and Winnebago County must map the
Flood Storage District areas in order for the new FIRMs to take effect,which will be done as part of
one overall request in 2019. Once the Zoning Ordinance is amended to include the Flood Storage
Districts, staff will start the mapping process with the County that will involve notification and
public meetings.
Mr. Gohde explained that the Flood Storage Districts are areas where water is currently
accumulating. He said currently,rural detention areas are not calculated into the floodplain. He
explained that the floodplain kept growing every year but if the rural detention areas were
included in the calculation, the floodplain in many areas could decrease. He reiterated that the
volume of water in the Flood Storage District has to be maintained and cannot change.
Mr. Fojtik stated this item will impact many homeowners even himself. He said this affects him
because a portion of his lot is located in the floodplain and therefore he needs flood insurance.
Mr.Mott asked for confirmation that only the amendment to create a Flood Storage District in the
ordinance was being approved and not the map.
Mr.Burich confirmed. He stated the mapping will occur next year.
Mr.Mott and Mr.Fojtik asked about the sizes of the red areas (Flood Storage Districts) shown on
the map.
Item-Text Amendments-Zoning Ordinance 4
Mr. Gohde explained that the red areas are what current data is showing as areas that are
detaining water whether they are detention basins, culverts or low spots.
Mr.Mott asked if the map shown will change.
Mr.Burich replied the map is a proposal of where Flood Storage Districts will be mapped. He
explained there are multiple steps. He said the City would map areas within the city and the
County would map areas outside of the city.
Mr.Mott asked if staff foresees a change in the rainfall events by adding the Flood Storage
Districts.
Mr. Gohde replied that the Flood Storage Districts are taking into account the 100 year rainfall
event which is what FEMA is requiring.
Mr. Mott asked if the map needed to be change later,that it could be changed.
Mr. Gohde replied it could be changed.He said if the rainfalls change,the City can work with
Winnebago County and amend the Flood Storage Districts. He stated that FEMA is not
approving the Flood Storage Districts but only requiring them.
Bernie Pitz,617 W.Irving Avenue,stated that he owns land along Sawyer Creek. He said he made
two trips to City Hall to find out more information on the mapping. He said he stopped in Planning
and Zoning as well as Public Works and no one had information for him. He stated that there were
two publications on it directing questions to Planning and Zoning. He stated that the item should
be laid over until information and maps can be provided to the general public.
Ms. Propp reiterated that the map is not being approved, only the creation of the Flood Storage
District in the ordinance is being approved. She agreed with Mr.Pitz is regard to giving the
proper information,maps and notices to the general public at the time of mapping the Flood
Storage Districts.
Mr.Burich agreed. He said originally,there was a meeting scheduled but it was cancelled due to
unforeseen circumstances. He stated there is a meeting scheduled around the end of January to
February with all affected property owners. He said the meeting will be held before it comes to
Plan Commission for any action.
Motion by Bowen to approve the public hearing:proposed zoning ordinance amendment to create Flood
Storage District within section 30-156 of the Floodplain Overlay Zoning District.
Seconded by Kiefer. Motion carried 8-0.
Item-Te,rt An:endn:etets-Zoning Ordinance 5
City of Oshkosh Zoning Ordinance Municipal Code
FEMA before it is effective. No changes to regional flood elevations (RFE's)on
non-FEMA maps shall be effective until approved by the DNR. These maps
and revisions are on file in the office of the Zoning Administrator, City of
Oshkosh. If more than one map or revision is referenced, the most current
approved information shall apply.
(a) Official Maps:Based on the FIS.
(i) Flood Insurance Rate Maps (FIRM), dated 3/17/2003; with
corresponding profiles that are based on the Flood Insurance Study
(FIS) dated 3/17/2003. Approved by: The DNR and FEMA
(3) Establishment of Districts.The regional floodplain areas are divided into three
districts as follows:
(a) The Floodway District (FW) is the channel of a river or stream and those
portions of the floodplain adjoining the channel required to carry the
regional floodwaters.
(b) The Floodfringe District (FF) is that portion of the floodplain between the
regional flood limits and the floodway.
(c) The General Floodplain District(GFP)is those areas that have been or may
be covered by floodwater during the regional flood.
(d) The Flood Storage District (FSD) is that area of floodplain where storage
of floodwaters is calculated to reduce the regional flood discharge.
(4) Locating Floodplain Boundaries. Discrepancies between boundaries on the
official floodplain zoning map and actual field conditions shall be resolved
using the criteria in paragraphs (a) or (b) below. If a significant difference
exists, the map shall be amended according to Section 30-156(K). The zoning
administrator can rely on a boundary derived from a profile elevation to grant
or deny a land use permit,whether or not a map amendment is required. The
zoning administrator shall be responsible for documenting actual pre-
development field conditions and the basis upon which the district boundary
was determined and for initiating any map amendments required under this
section. Disputes between the zoning administrator and an applicant over the
district boundary line shall be settled according to Section 30-156(J)(3)(c) and
the criteria in (a) and (b)below.
(a) If flood profiles exist, the map scale and the profile elevations shall
determine the district boundary. The regional or base flood elevations
shall govern if there are any discrepancies.
--------------------------------------------- --------- -----------------------------------
City
---------------------------•----- -----------------
City of Oshkosh Chapter 30-Page 223 Municipal Codes
Page 5
City of Oshkosh Zoning Ordinance Municipal Code
(c) Transmit one copy of the information described in pars. (a) and (b) to the
Department Regional office along with a written request for technical
assistance to establish regional flood elevations and, where applicable,
floodway data. Where the provisions of Section 30-156a)(1)(b)(iii) apply,
the applicant shall provide all required information and computations to
delineate floodway boundaries and the effects of the project on flood
elevations.
(I) Flood Storage District
(1) General. The flood storage district delineates that portion of the floodplain
where storage of floodwaters has been taken into account and is relied upon
to reduce the regional flood discharge. The district protects the flood storage
areas and assures that any development in the storage areas will not decrease
the effective flood storage capacity which would cause higher flood
elevations.
(a) Applicability. The provisions of this division apply to all areas within
the Flood Storage District as shown on the official floodplain zoning
maps.
(b) Permitted Use.Any structure,land use, or development is allowed in the
underlying zoning district if the standards in Section 30-156(1)(c) are met,
the use is not prohibited by this or any other Ordinance or regulation and
all permits or certificates specified in Section 30-156(K)have been issued.
(c) Standards for development in Flood Storage Districts
(i) Development in flood storage district shall not cause an increase
equal or greater than 0.00 of a foot in the height of the regional flood.
(ii) No development shall be allowed which removes flood storage
volume unless an equal volume of storage as defined by the pre-
development ground surface and the regional flood elevation shall be
provided in the immediate area of the proposed development to
compensate for the volume of storage which is lost (compensatory
storage).
(iii) If compensatory storage cannot be provided, the area may not be
developed unless the entire area zoned as flood storage district- on this
waterway- is rezoned to the floodfringe district. This must include a -
revision to the floodplain study and map done for the waterway to revert
•-------------------------------------------------------------
City of Oshkosh Chapter 30-Page 236 Municipal Codes
Page 6
City of Oshkosh Zoning Ordinance Municipal Code
to the higher regional flood discharge calculated without floodplain
storage, as per Section 30-156 (L) of this chapter.
(iv) No area may be removed from the flood storage district unless it
can be shown that the area has been filled to the flood protection
elevation and is contiguous to other lands lying outside of the
floodplain.
(J) Nonconforming Uses.
(1) General
(a) Applicability. If these standards conform with Section 62.23(7)(h), Stats.,
they shall apply to all modifications or additions to any nonconforming
use or structure and to the use of any structure or premises which was
lawful before the passage of this Ordinance or any amendment thereto.
(b) The existing lawful use of a structure or its accessory use which is not in
conformity with the provisions of this Ordinance may continue subject to
the following conditions:
(i) No modifications or additions to a nonconforming use or structure
shall be permitted unless they comply with this Ordinance. The
words "modification" and "addition" include,but are not limited to,
any alteration, addition, modification, structural repair, rebuilding
or replacement of any such existing use, structure or accessory
structure or use. Ordinary maintenance repairs are not considered
an extension, modification or addition; these include painting,
decorating, paneling and the replacement of doors, windows and
other nonstructural components and the maintenance, repair or
replacement of existing private sewage or water supply systems or
connections to public utilities. Ordinary maintenance repairs do not
include any costs associated with the repair of a damaged structure.
The construction of a deck that does not exceed 200 square feet and
that is adjacent to the exterior wall of a principal structure is not an
extension, modification or addition. The roof of the structure may
extend over a portion of the deck in order to provide safe ingress and
egress to the principal structure.
--------------------------------- - - - -- - -
City of Oshkosh Chapter 30-Page 237 Municipal Codes
Page 7
i
Flood Storage Area Frequently Asked Questions
Wisconsin Department of Natural Resources Floodplain Program
Q Why is this flood storage area information relevant?
In the process of developing new engineering studies for new floodplain maps and Flood Insurance
Studies (FIS), the flood storage capacity was considered for some waterways in your community where
detailed terrain data and significant flood storage exists.
Q.What is a flood storage area?
A flood storage area is part of the mapped floodplain that identifies the natural flood storage capacity
of that area in a watershed. A computer model was used to calculate the amount of runoff expected to
a mapped waterway within a watershed.The resulting volume of water is the basis for determining
how much of the regional flood discharge the flood storage area is capable of holding back. This
information is depicted on the FEMA floodplain map as the extent of the flood fringe areas.The
Department of Natural Resources will provide additional maps showing where flood storage was
considered within those flood fringe areas.
Q• What are the benefits of protecting flood storaae areas?
By infiltrating runoff water and acting as holding basins, flood storage areas can reduce the amount and
duration of flooding in the floodplain immediately downstream.Wetlands are a good example of natural
flood storage areas. If a wetland is filled, it can no longer provide this natural function and an increase
in flooding can be observed farther down in the watershed. Envision dropping a rock into a full glass of
water; the water spills out into surrounding areas that would otherwise be dry. By including flood
storage areas in the FIS,flood flows and floodplain elevations in lower reaches are reduced.
Q• How is the location of a flood storaae area determined and documented?
Engineers experienced in preparing floodplain maps and flood insurance studies evaluate areas
within the floodplain that could potentially provide a significant amount of flood water storage. Data are
collected from these areas and entered into the computer model calculations that are used to prepare
flood maps. By mapping and protecting the storage areas, the volume of flood waters can be reduced,
thereby lowering flood elevations in the floodplain. For current updates of the flood insurance studies,
flood storage areas are located where significant storage is provided by wetland areas mapped by the
Wisconsin Wetland Inventory, permanent impoundments (lakes or reservoirs) or immediately adjacent
areas.
Q How would a municipality know if they have flood storage areas and, therefore. need to
create a Flood Storage District in their zoning ordinance?
Before producing new floodplain maps, DNR will determine whether to include flood storage in the
study. They will notify all municipalities that have flood storage areas and then provide separate
Flood Storage District(FSD) maps that must be adopted into the floodplain zoning ordinance.The
DNR provides a model floodplain ordinance on its website that includes language for the creation of
Flood Storage Districts.This is located at: http•//dnr wigov/topic/floodplains/communities html.
Communities can choose to adopt the entire model ordinance or they can simply amend their existing
ordinance to adopt the new Flood Storage District maps and language.
Q.: What is shown on the Flood Storage Maps?
The Flood Storage Maps show the flood storage areas and the floodway. Only the floodfringe is
used to calculate the flood storage areas. Therefore, the flood storage areas do not extend beyond
the floodfringe as shown on the Flood Insurance Rate Map.
Page 8
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City of Oshkosh maps and data are intended to be used for general`identification City
purposes only,and the City of Oshkosh assumes no liability for the accuracy of the °f
information.Those using the information are responsible for verifying accuracy.For Printing Date: 12/11/2018 Oshkosh
full disclaimer please go to www.ci.oshkosh.wi.us/GlSdisclaimer Prepared by:City of Oshkosh,WI
LF CL J:\GIS\GIS_Base_Maps\Planning Base Map.mxd User:jeffn