My family and I are fortunate not to live in a designated floodplain. Designated floodplains are areas along our bayous that have a 1% annual chance of flooding. This diagram, adapted from the Harris County Flood Control District, illustrates the terminology we use to describe risk levels nicely:
The risks depicted in this graphic are from bayous flowing out of their banks due to large rain events. This does not illustrate the risks associated with large rainfall events exceeding the capacity of drainage systems serving local streets and neighborhoods.
In general, older drainage systems expose residents to higher risks of flooding while new drainage systems expose residents to lower risks of flooding. This is because a number of things have changed and improved over time. Our design standards have improved. Our knowledge of the location and depth of floodplains has improved. Our ability to measure ground surface elevations using laser technology has improved. Engineering practices have improved. That said, even the newest development — designed and built with the best engineering of 2017 — still has some risk of flooding from a large rain event. Current design standards accommodate the 1% annual chance rain event — about 12 inches of rain in 24 hours — anything more than that (or faster than that) may lead to structural flooding.
We have what I call legacy developments in the Houston region that were built before we had a national flood insurance program; before we mapped the 1% annual chance floodplains; and before we required flood mitigation of all new development in the form of detention basins. These are areas that have vibrant, economically productive communities; but they also have a higher risk of flooding than the current standard of practice.
We don’t have many options to address these legacy development areas and none of them are free. We could elevate all structures; buyout businesses and homes; retrofit or add new drainage systems (if the ground and flood elevations allow it); retrofit or add new detention facilities; or widen or deepen channels (again, if the ground and flood elevations allow it). Our public agencies are taking all of these actions almost all of the time, but the general public is not generally aware of this.
Due to our high rainfall, our flat topography, the age of much of our infrastructure, and the fact that we cannot implement a zero-risk approach to design — folks living in Houston should have flood insurance — whether you live in the floodplain or not.
You can check to see if you are located in the floodplain by typing in your address on this Federal Emergency Management Agency (FEMA) map search page. After the results pop up, just click on “View Map” (the magnifying glass icon) and zoom to your location. The legend explains all of the shading and codes.
If you are fortunate to not live the floodplain, the premiums are very affordable. Here’s a photograph of my current premium bill:
It cost much more to insure properties inside the 1% annual chance floodplain because the underwriter is exposed to a higher risk of loss. The underwriter for those policies is the U.S. National Flood Insurance Program (NFIP).
The premium charged by NFIP does not, however, reflect the true risk of loss, because members of the United States Congress tend to keep the premium costs subsidized so they can be re-elected. This has led to the NFIP Trust Fund to be periodically strapped for cash, as recently reported in the Houston Chronicle. Perhaps I’ll post on this topic another day.
Are you in – or out – of the floodplain? If you are out of the floodplain, how close to the 1% floodplain is your home located? If you are located outside the floodplain do you purchase insurance?