The Whole Storm Water Picture: How Innovation is Helping a City See It

storm-water-planningWith flooding often occurring from everyday rainfall in Houston, having a comprehensive view into drainage capacity is critical for Texas’ largest city. Using an innovative approach and GIS-based technology, RPS Klotz Associates helped the city economically achieve a more complete and accurate picture of its storm water network, with exponentially improved data accuracy.


Houston lies on a coastal plain less than 45 feet above sea level and experiences more than 100 days and 50 inches of rainfall annually, on average. While flooding in most U.S. cities occurs due to extraordinary storm events, flooding in parts of Houston happens frequently with everyday rainfall.

Challenged like many cities with maintaining an aging infrastructure system for its growing population, city staff uses a computerized toolbar – created by RPS Klotz Associates in 2009 – to prioritize infrastructure projects. In 2014, the tool only included verified data on closed conduits that comprise 62 percent of its drainage network. The roadside ditches that make up the remaining 38 percent were included through capacity assumptions. Further, the tool’s analysis only provided a pass/fail grade on flooding probability for two-year storm events (50 percent probability), and not more severe events, such as 2008’s Hurricane Ike (a 100-year event with a 1 percent probability).


To resolve the issue and provide a more comprehensive picture, we helped the city leverage a topographic survey planned by another city department to economically update the infrastructure tool. Whereby manual surveying to add roadside ditches to the toolbar would cost millions, our Design Event Adequacy analysis used GIS-based modeling to cost-effectively automate programming data.

Using an innovative approach, our engineering team overlaid existing standard data sets with new survey data to more accurately reflect actual conditions, both underground and above ground. Working with existing data from FEMA, county property records and the city’s online maps, we analyzed the data via a computer script to identify and fill in data gaps using the new data. Moreover, the team reconfigured the automation code used on the roadside ditch network and developed methodologies to analyze the closed conduit system, allowing a more detailed level of adequacy to be assigned to the entire storm drainage network.


A significant breakthrough in drainage evaluation techniques, our Design Event Adequacy analysis enables the City of Houston to pinpoint the inadequacy of one or more components within an interconnected drainage system and identify right-sized corrective measures. It also helps the city better predict the ability of the system to handle a wider range of storm events.

Awarded a Gold Medal in the American Council of Engineering Companies 2016 Texas Engineering Excellence Awards, this GIS-based computer tool revolutionizes storm water planning and enables the city to budget investment in areas of greatest need and cost-effectively plan for the long term.

For more information on Design Event Adequacy and how this concept may apply to your projects, contact us.