Tuesday, July 8, 2008

FEMA Flood Maps Needed to Be Updated

Subject: Updating FEMA flood maps> Date: Mon, 7 Jul 2008 14:18:26 -0500> Take a look at this publication: http://wa.water.usgs.gov/pubs/ofr/floodgis/ This is a case study of an effort to update the flood maps of> the region around Olympia Washington. It includes a discussion
of the methodolgy used to update the maps and a good summary, in the introduction, of the problems with the existing 1980's vintage flood maps. We need a flood map update. Not only that, we need this update before serious efforts are made to elevate or floodproof structures in Mosquito Flats. It's really foolish to put lots of money into elevating a structure to the FEMA / flood-plain ordinance imposed one foot above the 100-year flood level, if that level is itself a pipe-dream. Houses that are gutted to the bare studs are at the right point to consider elevating, as was done for 840 Normandy Drive after the flood of '93. (That house had water over the kitchen counters in that flood.) With the studs bared, they attached temporary horizontal wooden beams to the studs along all the walls, then threaded I-beams through the house from side to side and used these beams to lift the structure off the slab foundation. Then, they built a new foundation of concrete block up to the house's new height, put a frame floor on the foundation, and then lowered the house onto that floor. But, before doing this, you need a target elevation!

1 comment:

marigolds6 said...

That information predates the FEMA Flood Map Modernization program.
http://www.fema.gov/plan/prevent/fhm/mm_main.shtm

Look up the status for Iowa here:
http://www.floodmaps.fema.gov/fhm/scripts/ST_srch.asp?state=IA
The Johnson County county-wide dfirm was updated 02/16/2007.
One very important drawback to map corrections is that flood insurance rates go up dramatically after a map correction for houses that are placed into the 500 year flood plain or are changed from the 500 year flood plain to the 100 year flood plain.