Flood Early Warning System

Bandera County River Authority and Groundwater District

Flood Early Warning System

Floods are the leading cause of natural disaster losses in the United States. Although loss of life to floods during the past half century have declined, in part because of improved warning systems, economic losses have continued to rise with increased urbanization in flood hazard areas throughout the nation (U.S. Geological Survey, 2006).

While floods are impossible to prevent completely, and there is no way to guarantee the protection of life and property, many federal, state, and local agencies have demonstrated that the loss of life, injuries, and property damage can be greatly reduced with a FEWS in place.

Over the past 30 years, the average statistics show annual flood losses in the United States at about $8 billion and nearly 100 fatalities per year. Bandera County is in the Texas Hill Country region, where high-intensity rain rates and steep terrain frequently contribute to flash flooding (Caran and Baker, 1986). Bandera County River Authority and Groundwater District (BCRAGD) was approved for and received cooperative agreement funding grants from the Texas Water Development Board (TWDB) to contract with a third-party Federal Contractor, the U.S. Geological Survey (USGS) for the development of two Flood Early Warning System (FEWS) for Bandera County, Tx. The FEWS’s were a 3-year data collection and development period each and included additional USGS stream gage installations for monitoring and the assembly of near real-time streamflow data. A FEWS initial study area was completed (May 2019) that encompassed a 23-mile reach of the Medina River from the headwater confluence of Winans Creek to English Crossing Road above Medina Lake. Similarly, a FEWS study was completed (August 2023) for a 10-mile river reach of the Sabinal River in western Bandera County from Vanderpool, TX, to Uvalde County at Utopia, TX, and included portions of the West Sabinal River above Utopia, TX.

The USGS developed a Flood Inundation Map (FIM) of both FEWS’s using a Hydrologic Engineering Center-River Analysis System (HEC-RAS) hydraulic simulation model (U.S. Army Corps of Engineers, 2016 a, b). A flood atlas, consisting of a library of flood-inundation maps for a range of streamflow conditions, was developed and included on the USGS Flood Inundation Mapping Program (FIMP) website. The Flood Inundation Maps (FIMS) depict estimates of the areal extent and depth of flooding corresponding to selected water levels (stages) based on the USGS streamflow-gaging station 08178880 Medina River at Bandera, Tx bridge Highway 173 and the USGS streamflow-gaging station 08197970 Sabinal River at Utopia, Tx bridge FM-1050.

These flood-inundation maps, in conjunction with the real-time stage data from the USGS streamflow gages are intended to help guide the public in taking individual safety precautions and intended to provide emergency management personnel with a tool to efficiently manage emergency flood operations and post flood recovery efforts.

The FEWS provides near real-time hydrologic data, available on the internet and many other social media web-based outlets. A user can view data on river stage, flow, or rainfall in real-time, directly from the streamflow-gaging station using the internet, and can quickly access the specific flood map corresponding to the present river stage conditions. The flood atlas consists of a set of digital flood-inundation extent polygons and water depth grid maps derived from the gage height (river stage value), providing the user with corresponding land-surface inundation estimates and digital map overlays. Pre-defined user-set thresholds can be established for each available hydrologic monitored condition at the streamflow-gaging station, providing the user with email or text alerts when conditions reach or exceed a user-pre-defined threshold. This allows for critical information to be provided to the user preceding significant flooding conditions.

Flood Preparedness Resources

Streamgage Data

Flood Early Warning System (FEWS) Guidance Document for Texas

USGS National Water Information System https://waterdata.usgs.gov/nwis/

North Prong gage at Brewington Creek https://waterdata.usgs.gov/nwis/ inventory/?site_no=08178861

West Prong gage at Carpenter Creek Road https://waterdata.usgs.gov/nwis/ inventory/?site_no=08178871

Patterson gage https://waterdata.usgs.gov/nwis/ inventory/?site_no=0817887350

Bandera gage https://waterdata.usgs.gov/tx/nwis/ inventory/?site_no=08178880

USGS Texas Water Dashboard https://txpub.usgs.gov/ txwaterdashboard/

USGS WaterAlert https://water.usgs.gov/wateralert/

USGS Twitter

#TX RainWatch https://twitter.com/USGS_TexasRain

#TX FloodWatch https://twitter.com/USGS_TexasFlood

#USGS[streamgage number] (e.g. #USGS08178880)

National Weather Service River Forecast – only available for Bandera gage (USGS gage number 08178880, NWIS identifier BDAT2) https://water.weather.gov/ahps2/ hydrograph.php?wfo=ewx&gage=bdat2

Flood Inundation Maps

InFRM FDST: Interagency Flood Risk Management Flood Decision Support Toolbox.

Scientific Investigation Report

Flood Inundation Mapping Scientific Investigation Report

Flood Inundation Mapping Fact Sheet

USGS Data Release (Flood Inundation Map GIS files)

Public Hearings/Meetings

On January 12, 2017 BCRAGD held a Public Hearing on the Flood Early Warning System

On March 30, 2017 BCRAGD held a Public Meeting on the Flood Early Warning System

On October 28, 2017 BCRAGD held a Flash Flood Public Information Meeting

On January 4, 2018 BCRAGD held a USGS Flood Tool Set Status Meeting

On February 20, 2018 BCRAGD held a USGS Flood Tool Set Status Meeting

On November 28, 2018 BCRAGD held an informational Public Meeting on the Flood Early Warning System

On February 26, 2019 BCRAGD held a Public Meeting on Medina River Flood Early Warning System

On February 26, 2019 BCRAGD held a Public Meeting on Upper Sabinal River Flood Early Warning System

Local Flash Flood Information Resources

Click below on parts 1-3 for a presentation by the National Weather Service given on October 28, 2017 at the Flash Flood Public Information Meeting.

Flood Inundation Maps Click below for the latest update of the Flood Warning Project, presented by BCRAGD in cooperation with USGS on October 28, 2017 at the Flash Flood Public Information Meeting.

Miscellaneous Information

Final Report to TWDB for the completion of the Medina River Flood Early Warning System: TWDB Final Report Medina FEWS Contract No. 1600012035

Bandera County

River Authority &
Groundwater District

Drought Status: Severe

CALL US: (830) 796-7260

CALL US: (830) 796-7260

Drought Status: Severe

Bandera County

River Authority & Groundwater District

Drought Status: Severe

CALL US: (830) 796-7260

Bandera County

River Authority & Groundwater District

Flood Early Warning System