Although the Austin area has been in drought for much of the past 10 years, if you have been around Austin for a while, you know that floods also feature prominently in our history. The Memorial Day Flood of 2015 was especially memorable, but there have been many more. Were you here for the Memorial Day Flood of 1981? That one led to major changes in the city, especially along Shoal Creek and South Lamar, but all of Austin was affected. Going back even further there were many more.
You also undoubtedly know that the Austin area has been growing fast for many years. As the Austin Chronicle noted in 2017, As Austin Grows, So Does the Risk of Flood. More people, more buildings, and more impervious cover combine to raise the risk of flooding.
Compounding that increased risk, based on a study by the National Weather Service, the likelihood of heavier rain is higher now than in the past. The historical definition of a 100-year storm was a little more than 10 inches of rain in 24 hours. That means that each year there is a 1% chance of that kind of rain event. The new study indicates that there is now a 1% chance each year of 13 inches or more rain falling in 24 hours. (That has been the definition of a 500-year storm.) The revised 25-year floodplain will also expand in some areas, taking on properties that are now in the 100-year floodplain.
So … with the combination of growth and more rain the City of Austin is reassessing local flood maps. Obviously, the most severe changes will be along and near existing flood zones, and the number of structures that are in officially flood-prone areas will increase from about 4,000 now to 7,200 on the new maps. In many cases, properties that have been in the 500-year floodplain will be reassigned to the 100-year floodplain, and structures in the 100-year floodplain will now be in the 25-year floodplain. This is really dramatic change! Until the maps can be completely redrawn, City code will be modified to restrict what property owners in the 500-year floodplain can do with their properties, effectively moving them immediately into the 100-year floodplain. For more on this and to find out if your property is affected, see Flood Risk and Atlas 14.
Note that updating local flood maps won’t directly or immediately change FEMA flood maps, but there can’t be any doubt that those maps will change as well. That means that more property owners with mortgages will be required to carry flood insurance. Not only does that add expense to property ownership, but it will likely affect resale values and even sale-ability. That’s another topic for another day, but don’t underestimate its importance!
Over the past couple of years, the Austin Board of REALTORS®, the Texas Association of REALTORS®, and the National Association of REALTORS® have all be working to get the National Flood Insurance Program reauthorized by Congress. There have been short-term extensions, but the latest one expires in November 2018. We have argued that more sophisticated maps are necessary and that premiums should more accurately reflect insured risks, along with more changes to make the program financially sustainable. It is an extremely important program, however, and reauthorization needs to be done. For more information on that see this article about the National Flood Insurance Program from the National Association of REALTORS®.