Flood-mitigation best practices, flood depth

Three Flood-Mitigation Best Practices That Could Help Houston Region

On 3/22/23, I attended a lunchtime seminar on flood-mitigation best practices hosted by FEMA Region 3 (Philadelphia, Baltimore, Washington DC). The topics covered included building hazard-mitigation plans, resiliency hubs, and flood awareness programs.

The seminar showed dozens of excellent thought-provoking ideas – too many to list in one post. But three in the last category (awareness) really jumped out at me. I will share them below.

It Was How Deep!

This bright display below in a little pocket park shows the depth of flooding during historical and statistical (i.e., 100-year and 500-year) floods. The historical floods go back to 1937.

Image courtesy of FEMA

That will certainly keep people from forgetting.

How Deep Could It Get at My Home or Business?

Flood Depth Grids are a related idea. They go far beyond the types of flood maps we currently rely on that show flood frequency zones, like the 100-year (1% annual chance) flood zone. These answer the question, “How deep would the water get in a 100-year flood?” In this case, 2.88 feet of water would invade the building shown beneath the pointer.

Image courtesy of FEMA

This gives people additional useful information they can use to protect their homes and businesses from flood losses. For instance, how high do I need to elevate my home? Or how high do I need to elevate critical machinery used in my business? That’s far more useful than just knowing whether you’re in a zone that has a 1% annual chance of flooding.

How Much Damage Could I Expect?

The flood-mitigation best practice took that flood-depth information to the next level. It answers the question, “If we get a 100-year flood, how much damage would it do to my structure?”

The screen capture below shows a highlighted home on the right. The box on the left shows the assessed value of that home. And at the bottom in blue, it shows the estimated damage in dollars to that structure based on a flood that deep.

Image Courtesy of FEMA

Good or Bad for Property Values

Not everyone will like these ideas. Some might say they could affect property values negatively. But they also could affect property values positively. How? By giving people valuable information they need to protect themselves.

For instance, some people may feel they don’t need flood insurance. Two thirds of the people flooded in Harvey felt that way. But seeing those brightly colored markers dangling at the height of a basketball hoop could motivate you to get flood insurance. And that could protect your neighborhood from abandoned, derelict homes like we still see all over Houston five years after Harvey. All said, I’d personally rather know than not know.

These best practices could help in another way, too – by motivating home and business owners to keep up the pressure on political leaders to mitigate flood risk. Going a few years without a flood can lull people into believing their risk has been mitigated when it hasn’t.

Personalizing Risk

Getting a couple feet of water in my house sounds bad. But losing $168,700 dollars in the process really grabs my attention!

If you saved $200 dollars per month, it would take 500 months (41.6 years) to save just $100,000. During that time, you would have a 34.2% chance of experiencing a hundred year flood. Yep! More than one in three! Check out this flood risk calculator by the National Weather Service.

That kind of knowledge makes people think much harder about how much flood risk they take on.

MAAPnext Will Provide Similar Information

Harris County Flood Control District (HCFCD) currently has an ongoing effort called MAAPnext. It will provide similar information to residents in Harris County.

However, FEMA is reportedly still vetting all the LIDAR data and calculations. FEMA should release the new information sometime this year. They will not pin a date down closer than that.

Posted by Bob Rehak on 3/27/23

2036 Days since Hurricane Harvey

Six of ten wettest cyclones in US history struck SE Texas

Intro to Flooding in Southeast Texas

Jeff Lindner, Harris County’s Meteorologist, has produced an excellent 20-minute video that explains flooding in Southeast Texas and how you can increase your situational awareness during extreme weather events. It’s now on YouTube and is called “Understanding Flooding in Southeast Texas.”

By Jeff Lindner, Harris County Meteorologist

Brief Outline of Video

The video begins with a description of things that make this area unique – namely extreme rainfall on flat topography.

Then Lindner begins by reminding us of extreme rainfalls, such as Tropical Storm Claudette in 1979 which set the U.S. 24-hour rainfall record – 43 inches in one day! To put that in perspective, it took Hurricane Harvey FOUR days to dump 47.4 inches.

Tropical Storm Allison in 2001 dumped 28.5 inches in just 12-hours. It turns out that…

Six of the ten wettest tropical cyclones ever to strike the US mainland struck Southeast Texas!

Jeff Lindner, Harris County Meteorologist
Video is signed for hearing impaired

Then the video:

  • Defines watersheds, describes local watersheds, and explains how water flows throughout Harris and surrounding counties
  • Discusses ponding and sheet-flow flooding, unrelated to watersheds
  • Explains how streets are designed as part of the floodwater retention system
  • Talks about the Harris County Flood Warning System and the distribution of gages in surrounding counties
  • Digs into some of the System’s features, such as Near-Real-Time Inundation Mapping
  • Tells you how sign up for Notification Alerts and explains different types of alerts you can set
  • Reviews the limitations of home insurance and flood insurance policies.

Who Can Benefit from Watching?

Many types of people can benefit from watching this video:

  • People new to the area
  • Young people
  • Anyone buying property or new homes
  • Long-term residents who have had close calls during previous floods
  • Those without flood insurance or those considering buying it.

Regarding insurance, Lindner reminds us that it takes 30-days for flood insurance to go into effect and that you can’t buy flood insurance when there’s a named storm in the Gulf. So the time to buy it is well before hurricane season, which starts on June 1.

It’s also important to remember that flooding can happen in non-tropical storms that occur in virtually any month of the year. Tax Day and Memorial Day storms are good examples. The Tax Day storm dumped 23.5 inches of rain in 12-hours!

Of the 154,170 estimated homes that flooded across Harris County during Harvey, only 36% had active flood insurance policies in place the day before the storm struck…64% did not have flood insurance.

If you think that government disaster relief will make you whole soon after a flood, think again. Five and a half years after Harvey, people are still waiting for aid or in the process of rebuilding their homes.

Posted by Bob Rehak on 3/26/2023

2035 Days since Hurricane Harvey

weather-related disasters causing more than $1 billion in damage since 1980.

Tropical Cyclones Costliest Type of Weather-Related Disaster By Far

Since 1980, tropical cyclones have been the costliest type of weather-related disaster in the United States, according to NOAA’s National Centers for Environmental Information (NCEI). The NCEI study includes events that caused at least one billion dollars in damages when adjusted for inflation.

Accounting for just under a fifth (17.6%) of the total number of events, tropical cyclones have caused more than half (53.8%) of the total damages.

Tropical cyclones also cause more deaths than any other type of weather-related disaster.

Types of Events Compared

NCEI monitors the following types of disasters:

  • Hurricanes
  • Drought
  • Inland floods
  • Severe local storms
  • Wildfires
  • Crop freeze events
  • Winter storms

Damages Quantified

Since 1980, the U.S. has sustained at least 341 billion-dollar, weather disasters (including Consumer Price Index adjustment to 2022). The total cost of these 341 events exceeds $2.4 trillion.

Out of that total, tropical cyclones have caused a combined $1.3 trillion in total damages—with an average of $22.2 billion per event. They leave droughts in the dust. Droughts are the second costliest.

Rank ordered based on average cost per event, they line up like this:

  • Tropical Cyclones – $22.2 billion
  • Drought – $10.9 billion
  • Wildfires – $6.3 billion
  • Flooding – $4.8 billion
  • Winter storms – $4.3 billion
  • Freezes – $3.9 billion
  • Severe storms – $2.4 billion

The table below contains additional information about the frequency of billion dollar events, their total costs, and the number of deaths they cause.

NCEI Billion-Dollar Storm Statistics

No Region Immune

All parts of the county experience weather-related disasters. The dominant types of disasters vary by region. For instance winter storms are more costly in the north, droughts in the plains, and tropical cyclones along seaboards.

Cost of Disasters Increasing

Both the number and cost of billion-dollar weather-related disasters are increasing over time. Here’s the breakdown by year.

NCEI Billion Dollar Time Series 1980 through Jan. 2023

Reasons Cited for Increases

Exercise caution when interpreting the upward slope of the graph above. It would be easy to attribute the slope solely to climate change and many people will,

But NCEI points out that increases in population, and material wealth over the last several decades are an important factor for higher damages. So are the locations of population concentrations and failure to adopt better building codes.

“These trends are further complicated by the fact that many population centers and infrastructure exist in vulnerable areas like coasts and river floodplains, while building codes are often insufficient in reducing damage from extreme events,” says NCEI.

Data Sources

In calculating the cost assessments, we receive input from a variety of public and private data sources including:

  • Insurance Services Office
  • Federal Emergency Management Agency
  • U.S. Department of Agriculture
  • National Interagency Fire Center
  • Energy Information Administration
  • U.S. Army Corps
  • State agencies
  • Other partners

Costs Include…

Each of these data sources provides key pieces of information that capture the total, direct costs—both insured and uninsured—of weather and climate events. These costs include:

  • Physical damage to residential, commercial, and government or municipal buildings
  • Material assets within a building
  • Time element losses like business interruption
  • Vehicles and boats
  • Offshore energy platforms, electrical infrastructure, military bases
  • Public infrastructure like roads, bridges, levees, buildings
  • Agricultural assets like crops, livestock, and timber
  • Disaster restoration and wildfire suppression costs

One of the key transformations is scaling up insured loss data to account for uninsured and underinsured losses, which differs by peril, geography, and asset class.

Costs Do Not Include…

However, these loss assessments do not take into account losses to natural capital or assets, health-care-related losses, or values associated with loss of life. Therefore, consider NCEI estimates conservative with respect to what is truly lost, but cannot be completely measured.

Posted by Bob Rehak based on Information from NCEI

2034 Days since Hurricane Harvey