Onion Creek Flooding, 30 October 2013

Number of buyouts by the City of Austin in the Onion Creek area – 323 homesApproximate amount spent on buyouts - $36 million ($8M of this from FEMA grant funding)

A flooded home location

FEMA Flood Hazard Zone

Drainage Area above HomeDrainage area = 732 km2, or 282 miles2

Variation in SLOSH Model Storm Surge Elevations at Developed Shoreline

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

Shoreline Locations - Not to scaleSt

orm

Sur

ge E

leva

tion

(ft m

sl)

Cat 5Cat 3Cat 1

PRELIMINARYsource: FEMA MAT, 2-26-06

Flood Water Elevations

Halloween Flood on Onion Creek Expected Hurricane Storm Surge Heights on Gulf Coast

Halloween Flood ~ 120,000 cfs

Somewhere between 20 yr and 100 yrreturn period, perhaps 50 yrs

Halloween Flood

HEC-SSP Flood Frequency Analysisfull flood record

http://crhphotos.com/2013/10/halloween-2013-flood/