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<br />Appendix 3-C: Excerpts from Sample Flood Damage Prevention Ordinance, Prepared by <br />FEMA, Region X, Bothell, Washington. <br /> <br /> <br />5.2 STANDARDS FOR ALLUVIAL FANS <br /> <br />Areas subject to alluvial fan flooding have irregular flow paths that result in ero- <br />sion of existing channels and the undermining of fill material. Those areas are identified <br />on the Flood Insurance Rate Map as AO Zones with velocities. <br /> <br />I. All structures must be securely anchored to minimize the impact of the <br />flood and sediment damage. <br /> <br />C-18 <br /> <br /> <br />2. All new construction and substantial improvements must be elevated on pil- <br />ings, columns, or armoured fill so that the bottom lowest floor beam is ele- <br />vated at or above the depth number. <br /> <br />3. Use of all fill materials must be armoured to protect the material from the <br />velocity of the flood flow. <br /> <br />4. All proposals for subdivision development must provide a mitigation plan <br />that identifies the engineering methods used to: <br /> <br />a. Protect structures from erosion and scour caused by the velocity of <br />the flood flow. <br /> <br />b. Capture or transport flood and sediment flow through the subdivi- <br />sion to a safe point of deposition. <br /> <br />5. All mobile homes shall be prohibited within the identified hazard area ex- <br />cept within existing mobile home parks or subdivisions. <br />