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

Galveston

• Center for Texas Beaches and

Shores

• University of Maryland
• Center for Disaster Resilience
• Hagler Institute for Advanced

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
• 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

• Narrow definition: flooding that

can occur only in urbanized areas (i.e. sewer backup; flooding due to hydrologic modification

• Stormwater management
• Channelization
• Impervious surface
• Any exacerbation of normal

hydrology

• Broad definition: any type of

flooding that occurs in urban areas

• Types of flooding:
• Fluvial – natural (rivers, lakes,

etc.) or artificial (channel, detention basin, etc.) that breach or overspill onto adjacent areas.

• Pluvial – heavy rainfall that

exceeds natural or artificial drainage systems.

• Flash Flooding – extreme

rainfall on soils already 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.

CHANGING FLOODPLAIN BOUNDARIES

Source: City of Houston GIMS

AREAS SUBJECT TO PONDING

“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

• f damage have below

average income

• NFIP flood insurance

represented only 10%

• f total payouts

• The NFIP dataset includes

residential property insurance claims for building and contents 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.

Zone NFIP Claims in Urban Areas Number

Percent

SFHA 1075857

71.49%

Non- SFHA 429105

28.51%

Total 1504962

100%

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 Houston CBSA SHFA Claims 19,916 12,041 23,514 30,028 Dollars $551,592,016.86 $444,804,415.86 $950,934,969.94 $1,950,883,599.03 Non- SFHA Claims 18,871 13,034 23,884 23,072 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

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

Before Ike After Ike

THANK YOU