Which floods stand out in the record?
The Harris County Flood Control District keeps a flooding timeline that runs from 1900 to 2016. Five events recur in that timeline and in federal storm reports: December 1935, Tropical Storm Allison in 2001, the Memorial Day flood of 2015, the Tax Day flood of 2016 and Hurricane Harvey in 2017.
| Event | Dates | Rainfall | Reported impact |
|---|---|---|---|
| December 1935 flood | Dec. 6–8, 1935 | 16.49 in. at Satsuma; 5.52 in. in Houston | 8 drowned; $2.5 million in property damage |
| Tropical Storm Allison | June 2001 | 36.99 in. at the Port of Houston | 22 deaths; more than 70,000 structures flooded |
| Memorial Day flood | May 25–27, 2015 | Nearly 11 in. in three hours on Brays Bayou | 7 deaths; more than 6,000 structures flooded |
| Tax Day flood | April 17–18, 2016 | 12–16 in. in 12 hours | 7 deaths; an estimated 9,820 structures flooded |
| Hurricane Harvey | August 2017 | 36–48 in. across the Houston metro area | 36 direct deaths in Harris County; more than 120,000 structures flooded in the county |
What happened in 1935?
Torrential rain on Dec. 6–8, 1935, caused large rises on Buffalo and White Oak bayous, according to the U.S. Geological Survey. The flood control district’s timeline records Buffalo Bayou at 52 feet above normal. The flood led to the creation of the flood control district in 1937.
Why was Allison significant?
Allison struck in June 2001. NOAA’s Weather Prediction Center recorded its highest total, 36.99 inches, at the Port of Houston. NOAA estimated the damage at $5 billion, more than $4 billion of it in Texas. The flood control district counts 22 deaths and two million people affected. The USGS lists 23 deaths.
What were the 2015 and 2016 floods?
The Memorial Day flood of May 2015 dropped nearly 11 inches in three hours on the Brays Bayou watershed. The Tax Day flood followed in April 2016. Addicks and Barker reservoirs reached record pool levels. Houston Intercontinental Airport set a daily rainfall record of 9.92 inches. The USGS recorded peaks of record on Spring, Cypress and Willow creeks.
How large was Hurricane Harvey?
Harvey made landfall near Rockport in late August 2017. The National Hurricane Center reported 36 to 48 inches of rain across the Houston metro area. Its highest total, 60.58 inches, fell near Nederland. The flood control district reports that 1 trillion gallons fell on Harris County over four days. All 22 of the county’s watersheds were affected. The hurricane center counted 68 direct deaths in Texas, 36 of them in Harris County. NOAA estimated damage at $125 billion.
What changed after these floods?
FEMA published Flood Insurance Rate Maps for all 34 Harris County communities in 1985. In 2018, NOAA’s Atlas 14 study raised the 100-year rainfall estimate around Houston from about 13 inches to 18 inches. On Aug. 25, 2018, Harris County voters approved $2.5 billion in flood bonds. For current maps, see How do I find out if a Houston property is in a floodplain?