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River authority considering LiDAR mapping project

By Carolyn B. Edwards BCC Staff Writer

Pictured: LiDAR mapping can offer very detailed elevations, as this sample showing Six Flags and the Cotton Bowl illustrate.

The Bandera County River Authority and Groundwater District (BCRAGD) board is considering budgeting for a LiDAR mapping project that would create a database for clarifying flood plain boundaries and more.

The board heard a proposal from the San Antonio River Authority during a called meeting held Thursday, June 13. Melissa Bryant, SARA engineer, and John Refolo, SARA analyst, outlined the LiDAR mapping procedure and how it could be used as a part of the FEMA RiskMAP program.

SARA hopes to get BCRAGD on board as a participating sponsor of the program, meaning they are looking for funding partners. They hope to get $50K from the local river authority as Bandera County's part of the $230K cost of the mapping program.

BCRAGD General Manager Dave Mauk said he would approach other entities in the county to consider participating, such as Bandera County, the City of Bandera, Bandera Electric Cooperative, the Economic Development Corporation, and others.

The LiDAR mapping program is under the direction of the Texas Water Development Board. The acronym stands for Light Detection and Ranging. The process uses pulses of light from an airborne sensor to measure the elevation of the ground below. "It gives us four or more elevation points in a square meter," Rofolo explained, "yielding high quality elevation data."

Some parts of Bandera County have already been mapped, including the southeast border from Medina Lake eastward, a small block just north of Bandera along Highway 173, a swath in the center of the county that comes down from Kerr County, and a block in the Vanderpool area.

"SARA is working with the TWDB and the Edwards Aquifer Authority," said Bryant.

Once the LiDAR mapping is completed, SARA will use the data collected to participate in the FEMA RiskMAP program. RiskMAP is a nationwide project aiming to use high quality risk data to increase awareness of flood risk, promote community mitigation action and reduce risk to lives and property.

As participants in RiskMAP, BCRAGD would receive a Flood Risk Database, Flood Risk Report, and a Flood Risk Map. Datasets would include flood depth and analysis grids, flood risk assessments, and areas of mitigation interest. Bandera County is part of HUC 8, a classification number in the FEMA program, which includes the Medina River and Leon Creek watersheds. In the county, 5.31 miles of the watershed have been verified, with 399.19 miles still unknown.
The program will clarify flood plain boundaries and will be able to predict the percentage of risk for a location for 10-year to 500-year flood events, Refolo said.

"The LiDAR is data your community can utilize for many years, in various ways, say in emergency management," Refolo said.

Board member Jerry Sides urged a bit of caution before adding the project to the river authority's budget. "Let's see if we can get any money from anybody else before we budget." The board agreed.

The BCRAGD will meet on the third Thursday of of next month, July 18, for their regular meeting. The board meets at 9 am at the BCRAGD offices at 440 FM 3240.