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Chapter 6 Standards for Floodplain Development and Building Protection

Chapter 6 Standards for Floodplain Development and Building Protection

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Chapter 6 Standards for Floodplain Development and Building Protection

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  1. Chapter 6Standards for Floodplain Development and Building Protection

  2. Development is…... • Construction of new buildings • Addition or substantial improvements to existing buildings • Manufactured (mobile) homes and RVs • Subdivisions or commercial developments • Storage of materials • Fill, grading, excavating • Fences, culverts, bridges, roads • And ANYTHING else that changes the floodplain

  3. Standards of Floodplain Development Federal regulations at Subpart B, Section 59.22 (a)(3) require that communities adopt the minimum provisions of 44 CFR 60.3. These standards must be applied to all development and structures built or substantially improved in the SFHA.

  4. Building Protection Standards Methods to Elevate Buildings in an A Zone • Elevation on Fill • Elevation on flow-thru walls • Elevation by poles, piers, or columns

  5. Building Protection StandardsElevation on Fill Fill

  6. Building Protection Standards Elevation on Fill (cont.) Elevation on Fill • Before allowing floodplain fill, decide if the fill will increase flooding or cause drainage problems on neighboring properties.

  7. Building Protection Standards Elevation on Fill (cont.) Elevation on Fill • Before permitting floodplain fill, decide if the applicant plans to excavate a basement into the fill. Basements are not allowed in the SFHA! What is a basement?

  8. Building Protection StandardsElevation on Fill (cont.) • Usually limited to three or four feet in height • Fill placed in 6’ layers and compacted (95% proctor) • Extend fill 10’ around structure • Side slopes 1’ vertical to 1.5’ horizontal • Erosion control

  9. Building Protection Standards Elevation on Fill (cont.) House built on fill above the flood elevation

  10. Building Protection Standards Elevation on Solid Perimeter Walls Opening (typical)

  11. Building Protection Standards Elevation on Solid Perimeter Walls (cont.) • Types of solid wall foundations: • Chain walls • Perimeter walls • Unreinforced masonary block • Unreinforced brick • Some types are required to have flood vents

  12. Building Protection Standards Elevation on Solid Perimeter Walls (Cont.) • Enclosed areas below the lowest floor must have openings to equalize hydrostatic pressures (1” per 1 sq. ft.). • Openings no more than one foot above grade. • Flood resistant materials • NO HVAC, electric, utilities, etc..

  13. Building Protection Standards Elevation on Solid Perimeter Walls (cont.) Use of Enclosed Areas below the BFE • Parking • Limited Storage • Building Access

  14. Building Protection Standards Elevation on Solid Perimeter Walls (cont.) Flood-Resistant Materials • All materials below the BFE must be resistant to water damage. • TB 2-93 is the best source of information.

  15. Building Protection StandardsElevation on Solid Perimeter Walls (cont.) TB 1-93

  16. House built on elevated foundation walls Flow through crawl space

  17. Building Protection Standards Special Notes About Basements • Definition of a basement? • Can a crawl space be defined as a basement? • A “walk-out” basement is an enclosure below the BFE. What does that mean?

  18. What do you notice about the vents?

  19. Good vents?

  20. Building Protection Standards Elevation on Fill (cont.) • Example: In an area with a BFE of 6 ft, fill could be placed for 3 ft and chain wall or crawl space built for the additional 3 ft (plus any freeboard). Or, a combo of slab and raised floor.

  21. Building Protection Standards Elevation on Posts or Piles

  22. Building Protection Standards Elevation on Posts or Piles (cont.) Elevation on Post, Columns, Piers or Piles • Posts or columns are wood, steel, concrete, or masonry supports. • Piers are vertical structural members supported by concrete footings. • Piles are generally made of wood or prestressed concrete.

  23. Building Protection StandardsElevation on Posts or Piles (cont.) Piles

  24. Posts Piers

  25. Building Protection Standards Elevation on Posts or Piles (cont.) • Should be used in areas of deep flooding and/or high velocities (floodways) • Properly anchored to resist wind and water forces • Lower area must remain open (not enclosed later)

  26. House built on piers or poles above the flood elevation

  27. Building Protection Standards Crawlspace • Total height no more than 4 feet. • No more than 2’ below grade. • Flow through openings • Interior drainage controls • Flood resistant materials Technical Bulletin 11-01

  28. NOT in the Gulf States. Not while I’ve got a say!

  29. Building Protection StandardsCoastal High Hazard or V Zone Construction • Mean High Tide: All new construction in V Zones must be located landward of the reach of mean high tide. • Modification of Dunes: Prohibit man-made alteration of sand dunes in V Zones.

  30. Building Protection StandardsCoastal High Hazard or V Zone Construction (cont.) Methods to Elevate Buildings in a V Zone • New and substantially improved structures must have the bottom of the lowest horizontal member at or above the BFE.

  31. Building Protection StandardsCoastal High Hazard or V Zone Construction (cont.) • Bottom of the lowest horizontal structural member supporting the lowest floor

  32. Building Protection StandardsCoastal High Hazard or V Zone Construction (cont.) Methods to Elevate Buildings in a V Zone • A certificate of the design foundations for buildings in V zones is required to be submitted prior to permit issuance.

  33. Building Protection StandardsCoastal High Hazard or V Zone Construction (cont.) Coastal High Hazard Areas or V Zones • Structural Fill is prohibited to support buildings. • Nonstructural fill, such as might be used for landscaping, should be placed so that it does not divert waves and surging floodwaters onto other structures.

  34. FEMA Technical Reference

  35. Building Protection StandardsCoastal High Hazard or V Zone Construction (cont.) Connecting the Load Path in the V Zone • Continuous path from roof to wall to foundation • Materials that resist deterioration

  36. Building Protection StandardsCoastal High Hazard or V Zone Construction (cont.) V Zone / Breakaway Wall Certificate • In V Zones, the applicant must include the V Zone Certificate and an engineer’s certification of design on a breakaway wall.

  37. Building Protection StandardsCoastal High Hazard or V Zone Construction (cont.) Breakaway Walls (V Zone) • Minimum standard requires collapse after not less than 10 and no more than 20 pounds per square foot.

  38. Pre-Event 35

  39. Post-Event

  40. Building Protection StandardsCoastal High Hazard or V Zone Construction (cont.) Altering Sand Dunes • Your flood damage prevention ordinance prohibits manmade alterations of sand dunes that will increase potential flood damage. CoBRA • NFIP insurance not available. • You must still review and issue permits.

  41. Permit Issuance (continued) V Zones and Fill • Fill is not allowed as a method to elevate buildings in V Zones. • FEMA does not allow placement of fill in V Zones as a method to remove a site from the mapped floodplain by means of a LOMR-F. • Non-structural fill may be used for landscaping purposes and cannot divert waves and water toward any building.

  42. Building Protection StandardsManufactured Homes Manufactured Homes • Manufactured homes are treated the same as any other structure in the SFHA. Make it easy, require all units to be at or above the BFE!

  43. Building Protection StandardsManufactured Homes (cont.) Special Considerations • Manufactured Homes are extremely vulnerable to flood damage. • You may wish to require that a engineered foundation to ensure structural stability. • Anchoring, tie-down, & permanent foundation requirements must be outlined in the FP permit.

  44. FEMA 85 Sept. 1985