Josh Gunn, Ph.D. Center for Texas Beaches and Shores Texas A&M - PowerPoint PPT Presentation

Josh Gunn, Ph.D. Center for Texas Beaches and Shores Texas A&M University at Galveston April 19, 2017

 Introduction to team and NAS effort  People  Goals of project  Urban flooding problem  Defining urban flooding  Previous research efforts  Urban flooding trends in the U.S.  Specific look at Houston  Future work

 Texas A&M University at  Goals: Galveston  Better understand the causes and costs of urban flooding  Center for Texas Beaches and Shores  Identify impacts to vulnerable populations  University of Maryland  Provide specific and targeted  Center for Disaster Resilience policy recommendations to mitigate impacts of urban  Hagler Institute for Advanced flooding Study at Texas A&M University  National Academies of Sciences, Engineering and Medicine  Program on Risk, Resilience and Extreme Events Policy and Global Affairs  Urban flooding committee

 Types of flooding:  Narrow definition: flooding that can occur only in urbanized areas  Fluvial – natural (rivers, lakes, (i.e. sewer backup; flooding due to etc.) or artificial (channel, hydrologic modification detention basin, etc.) that  Stormwater management breach or overspill onto  Channelization adjacent areas.  Impervious surface  Pluvial – heavy rainfall that exceeds natural or artificial  Any exacerbation of normal drainage systems. hydrology  Flash Flooding – extreme  Broad definition: any type of rainfall on soils already flooding that occurs in urban areas saturated or with low permeability; can be a combination of fluvial and pluvial flooding upstream, but key is accumulation which causes flooding further down the watershed.  Coastal – Tidal or storm surge in coastal or deltaic areas.

C HANGING F LOODPLAIN B OUNDARIES

A REAS S UBJECT TO P ONDING Source: City of Houston GIMS

“The Prevalence and Cost of Urban Flooding: A Case Study of Cook County, IL.”  No correlation between damage payouts and floodplains  67% of zip codes with highest concentration of damage have below average income  NFIP flood insurance represented only 10% of total payouts

NFIP Claims in Urban Areas Zone Number Percent SFHA 1075857 71.49%  The NFIP dataset includes Non- residential property insurance SFHA 429105 28.51% claims for building and contents Total 1504962 100% damage from January 1, 1975 through December 31, 2014. It initially contained 2.068 million claims.  Focusing on contiguous U.S. and data cleaning reduced this to 1.87 million  Points were overlaid with 2010 U.S. Census that defined Urban Areas and points falling within this urban boundary were classified as urban.  Of the 1.87 million claims, 81% (1.5 million) are designated urban.

There has been a total of over $60 billion in damage claims in urban areas (in 2014 dollars) since the National Flood Insurance Program’s inception, with over $15 billion of that occurring outside of the regulatory floodplain

The number of insured flood claims in urban areas is increasing over time

The majority of claims annually are in the $5,000 to $50,000 damage range; the second highest number of claims are under $5,000

1975-1984 1985-1994 1995-2004 2005-2014 Claims 19,916 12,041 23,514 30,028 SHFA Houston Dollars $551,592,016.86 $444,804,415.86 $950,934,969.94 $1,950,883,599.03 CBSA Claims 18,871 13,034 23,884 23,072 Non- SFHA Dollars $438,669,396.93 $323,740,957.45 $830,512,718.06 $593,127,698.68

 Goals:  Better understand the causes and costs of urban flooding  Identify impacts to vulnerable populations  Provide specific and targeted policy recommendations to mitigate impacts of urban flooding  Need more data (and partnerships!)  Have:  NFIP  IA, PA, Buyout, HMGP, SBA (zipcode, back to ~2000  Need:  More spatially explicit data  Further back in time  Private insurance data

T HANK YOU The overall strategy is to keep the ocean surge out of Galveston Bay by using a coastal barrier (the Ike Dike) Before After Ike Ike