In Destin area of Florida I notice that the Gulf flood plain elevation is about 15 feet above sea level. Yet some of the areas just north of the beach dunes and ridge show flood plain elevations of about 8 feet above sea level, and they are shown NOT TO BE IN THE 100-YR FLOOD PLAIN.
My question is this: The 15-ft. elevation is obviously a storm surge, which is virtually an endless supply of Gulf water,and if a dune washes out, or a crevasse or connection forms (or exists), what is to keep water from getting to storm surge level in the areas at elevation 9 are shown not to be within the 100-year flood plain?
The 8-foot elevation seems about right, but I am highly concerned that a hurricane storm surge could wipe a condo out if it is at elevation 9 and 700 feet north of the dunes.
> In Destin area of Florida I notice that the Gulf flood plain elevation is about 15 feet above sea level. Yet some of the areas just north of the beach dunes and ridge show flood plain elevations of about 8 feet above sea level, and they are shown NOT TO BE IN THE 100-YR FLOOD PLAIN.
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> My question is this: The 15-ft. elevation is obviously a storm surge, which is virtually an endless supply of Gulf water,and if a dune washes out, or a crevasse or connection forms (or exists), what is to keep water from getting to storm surge level in the areas at elevation 9 are shown not to be within the 100-year flood plain?
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> The 8-foot elevation seems about right, but I am highly concerned that a hurricane storm surge could wipe a condo out if it is at elevation 9 and 700 feet north of the dunes.
The BFEs on velocity zones along the beach that go inland include wave effects on top of the storm surge effect (which is the Stillwater elevation in the Flood Insurance Study). The wave effects decrease as you go inland which decreases your BFE's as you go inland.
Hope this answers your question.
The Bow Tie Surveyor
Yes, I agree, and that works when the highest ridge is on the coast line. But when there is a coastal ridge on the beachfront, and then a low area and another ridge, the hydrology is completley different. A wave can only get to 60% of the water depth, but a wind-blown breaker with shoreline runup can get much higher, and if the duration of the surge and wind is long enough, the sump between the coastal ridge and the next ridge can get almost as deep as the Gulf level offshore outside the wave breaking zone. I was looking at buying a house there, and I noticed this landform and reviewed the FEMA map. The Gulf is shown to have flood level of 15 ft MSL, and the land between the two ridges is shown as 8 ft and is less than 700 feet from the gulf front. Not acceptable for me.