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HomeMy WebLinkAbout1806 - Floodplain Development & Storm Water Detention CITY OF REDDING, CALIFORNIA COUNCIL POLICY SUBJECT RESOLUTION POLICY EFFECTIVE NUMBER NUMBER DATE PAGE FLOODPLAIN DEVELOPMENT AND STORM WATER DETENTION 94-200 1806 7-5-94 I of 2 BACKGROUND In 1993, the City adopted t'he citywide Storm Drain Master Plan (SDMP), by Montgomery Watson Engineers. That st~dy covers the majority of streams in the City. The floodplain elevation findings of this study differ from those of the Federal Emergency Management Agency's (FEMA) study in that the effects of urban growth were estimated. The FEMA study looked at 1987 conditions only and assumed that future development in the watershed would not significantly alter flood flows. The City's 1993 SDMP estimates flood elevations based on the 1992 level of development and projects flood elevations based on full urbanization of watersheds. This situation has resulted in 'two distinct sets of floodplain data which could affect review and construction of projects in the City--one for "current" flooding conditions and one for the "future" conditions. Given that the City has existing tentative and recorded subdivision maps based solely on the FEMA data and will have new tentative maps submitted in the future, a determination must be made on which data will be used in each of the several circumstances. PURPOSE The purpose of this policy is to clarify which floodplain data will be used for projects to be constructed in the City. POLICY The following policies shall apply to those circumstances noted below. In all cases, the base flood elevations shall be those as determined by the 1992 elevations as shown on the SDMP or that level determined acceptable by the City Engineer based on specific studies, whichever is highest. 1. Recorded maps that have lots below FEMA and the SDMP lO0-year flood e/evat/ons. Structures shall be required to comply with the requirements of Chapter 18.47 of the Municipal Code (Floodplai~n Ordinance). Rezoning of property to the "FP" Floodplain District will be the principal implementation of this policy. 2. Recorded maps that have lots below the SDMP, but above the FEMA lO0-year flood elevat/on. Structures shall be required to have finished-floor levels raised above the 100-year flood elevation as determined by the SDMP or shall be subject to the flood-proofing requirement of Chapter 18.47. 3. Approved tentative maps based only on the l O0-year FEMA flood elevat/on. The subdivision may proceed as approved provided that all lots or building pads and streets are raised one foot above the 100-year flood elevation as determined by the SDMP and provided further that the fill to raise the lots does not cause increased flooding on other properties nor increase the flow velocity of the stream above the allowable limits contained in Chapter 18.47. The implementation of this section shall be through approval of improvement plans by the Director of Public Works or the is.~;uance of a grading permit by the City. 4. Tentat/ve maps not yet submitted. Unless a basinwide storm-drain plan has been approved and implemented to protect lots and property, the SDMP flood .elevation shall be used to process the tentative map and determine the 100-year floodplain, and the tentative map shall be subject to Chapter 18.47 and Article 17 of the Municipal Code. CITY OF REDDING, CALIFORNIA COUNCIL POLICY SUBJECT RESOLUTION POLICY EFFECTIVE NUMBER NUMBER DATE PAGE FLOODPLAIN DEVELOPMENT AND STORM WATER DETENTION 94-200 1806 7-5-94 2 of 2 5. Subdivision density and detention requirements for maps not yet submitted. a. FEMA l O0-year flood elevations shall be used to determine "Greenway" areas when determining 'Project density for tentative subdivision maps adjacent to the Sacramento River, streams, or drainages. The design of projects, however, shall be in accordance with Item 4 above. b. Where the City has adopted in its Land Use Element a channel configuration for a stream corridor that is less than the 100-year floodplain, the density credits for the area outside of the channel, but within any 100-year floodplain, may be granted to a developer subject to meeting the requirements of Chapter 18.47 of the City Code. Examples of this are Clover Creek and Olney Creek south of Sacramento Drive. However, such credit shall not result in lot sizes being reduced more than 25 percent below the lot size ranges as described in the Land Use Element of the General Plan nor shall it result in lot sizes below the minimum lot sizes established under the City's Zoning Ordinance (Title 18 of the Municipal Code). c. Measures shall be incorporated into project design to ensure that increases in storm-water runoff do not occur es a result of project construction and/or appropriate mitigation measures shall be inc. orporated into the project to lessen flooding elsewhere in the drainage basin. This requirement can be met through the use of detention or retention facilities--either on site or off site--or other measures as approved by the Planning Commission and the City Engineer. Exceptions to this subsection can be granted by the Planning Commission where it finds, based on hydrologic and other evidence provided by the applicant, that downstream properties will not be adversely affected by increased runoff resulting from development. The justification for exceptions shall include an assessment of the cumulative impact of construction on undeveloped properties within the watershed. 6. The City shall request that the jurisdictions of Shasta County and the City of Shasta Lake refer all project applications located in drainage basins common to both their jurisdictiOns and the City of Redding to thE; City for review and comment. It is the intent of this item that the above jurisdictions be requested to not approve projects which may increase flooding within Redding. 7. To accomplish the goal of determining the feasibility of regional detention facilities, City staff shall, on a yearly basis, submit appropriate budget proposals to the City Council for necessary drainage studies, land acquisitions, construction activities, or benefit-district formation. PROCEDURE The Planning Commission, the Department of Public Works, and the Department of Planning and Community Development shall implement these policies when considering subdivisions, use permits,~ building permits, rezonings, General Plan amendments, City construction projects, grading permit applications, and floodplain encroachments. 6-24-94 PROJ\POLICY\FP&STRMW.POL