I was just reading the National Hurricane Center’s Hurricane Ike Advisory, and this is not pretty:

SEVERE INUNDATION IS LIKELY NEAR THE IMMEDIATE COAST AND BAYSHORE AREAS!
NEIGHBORHOODS THAT ARE AFFECTED BY THE STORM SURGE…AND POSSIBLY ENTIRE COASTAL COMMUNITIES… WILL BE INUNDATED DURING THE PERIOD OF PEAK STORM TIDE. MANY RESIDENCES OF AVERAGE CONSTRUCTION DIRECTLY ON THE COAST WILL BE DESTROYED. WIDESPREAD AND DEVASTATING PERSONAL PROPERTY DAMAGE IS LIKELY. VEHICLES LEFT BEHIND WILL LIKELY BE SWEPT AWAY. NUMEROUS ROADS WILL BE SWAMPED… SOME MAY BE WASHED AWAY BY THE WATER. ENTIRE FLOOD PRONE COASTAL COMMUNITIES WILL BE CUTOFF. COASTAL RESIDENTS IN MULTI-STORY FACILITIES RISK BEING CUTOFF. CONDITIONS WILL BE WORSENED BY BATTERING WAVES CLOSER TO THE COAST. SUCH WAVES WILL EXACERBATE PROPERTY DAMAGE…WITH MASSIVE DESTRUCTION OF HOMES… INCLUDING THOSE OF BLOCK CONSTRUCTION. DAMAGE FROM BEACH EROSION COULD TAKE YEARS TO REPAIR.

To get a comparative view of what this will potentially do to Texas, please see the Google Maps flood mashup below (view in own tab) by Alex Tingle which paints a bleeck picture:
http://flood.firetree.net/embed.php?ll=29.3337,-94.8820&z=6&m=3&w=600&h=600
The city of Galveston was wiped off the map during the Hurricane of 1900 killing between 6,000 and 12,000 people. In response the city rebuilt itself around a Galveston Seawall which tops out at 17 feet above sea level and raised the mean city level as much as 17 feet.