Heavy rains bring flood mitigation to front of mind this time of year, causing some readers to wonder how the city determines which parts of Austin fall into designated floodplains, or areas likely to flood when creeks rise and flow over their banks.
Katina Bohrer, engineer with the city’s watershed protection department, said determining the location and shape of a floodplain involves four steps:
- The department obtains topology data for a creek, which reveals its depth and width.
- Next it must determine how much water is getting to a creek by estimating how much water is expected to run off the land and into the creek during a specific flood event.
- Then the department analyzes how deep the water would be once the runoff reaches the creek.
- Once the depth of the creek during a specific flood event is determined, the depth is drawn on a contour map to understand where the water will go and how far it will spread.
