Tuesday, September 5, 2017

Hurricane Harvey and Central Texas

Hurricane Harvey and Central Texas

Hurricane Harvey made landfall on the Texas Gulf Coast late Friday, bringing with it one of the most disastrous floods in the state’s history. From Corpus Christi and Rockport to Houston and La Grange, wind and rainfall from the storm caused damage and displacement on a catastrophic scale. Houston alone received over 51” as of August 31st. That’s the greatest amount ever recorded in the Lower 48 states from a single storm.

The effects of Harvey have extended to Central Texas. Specifically, regarding rainfall:
  • Buda saw 11.7” according to LCRA Hydromet
  • Manchaca received 9.6” according to BSEACD gauges
  • Driftwood recorded 7.4” according to LCRA Hydromet
  • Austin (Mabry: 5.9”, ABIA: 6.2”) got roughly 6” (KXAN weather diary)
  • Wimberley took 5.3” according to LCRA Hydromet

While rain was nearly constant in the region beginning Friday evening and continuing into early Monday, the effects on the stage level of local creeks and rivers might seem unexpectedly subtle. Although all saw a rise in stage and flow, none achieved flood status as a result of the downpour.

Top Stage Level Reached 8/27/17
Historic (H)/Flood (F) Stage Level
2015 Memorial Day Flood Stage Level
Blanco River at Wimberley
13 (F)
Onion Creek at Driftwood
5.5 (F)
Onion Creek at Twin Creeks Rd
22 (H)
Williamson Creek at Manchaca Rd
21 (H)
Barton Creek above Barton Springs
18 (H)

Springflow at Barton Springs
saw a slight increase of five cubic feet per second (cfs) while Jacob’s Well Spring measured a 40 cfs increase.

Water levels in the Barton Springs Edwards Aquifer Conservation District
(BSEACD) Lovelady monitor well were declining until the rain event brought stabilization. 

Onion Creek at Driftwood saw a quick climb to around 210 cfs late Sunday (8/27) night, though the peak was short-lived and never reached flood stage status.

The LCRA reports rainfall totals near the Highland Lakes ranged from less than an inch near Lake Buchanan to widespread totals of 2-4 inches near Lake Travis. This was not enough rain to make a significant difference in lake levels.
As Harvey drifted back toward the gulf late Sunday, rainfall decreased and stage levels began to quickly decline. After the deluge, the area received 9 inches in August, 7 inches above the average for the month.