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HomeMy WebLinkAboutItem VIPLAN COMMISSION STAFF REPORT DECEMBER 18, 2018 ITEM VI: PUBLIC HEARING: PROPOSED ZONING ORDINANCE AMENDMENT TO CREATE FLOOD STORAGE DISTRICT WITHIN SECTION 30-156 OF THE FLOODPLAIN OVERLAY ZONING DISTRICT 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 30-1.56 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. Item VI -Text Amendments -Zoning Ordinanee (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 (I), it will displace all the subsections below it which will also be renumbered as part of the amendment process. Item VI-TextAmendments Zoning Ordinance 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 30-156 as proposed. Item VI -Text Amendments -Zoning Ordinance 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 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 30-156(J)(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 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 storage 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 zonina 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.wi.gov/topic/floodplains/communities.htmi. 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