Lowering Costs and Improving Efficiency With 2D Stormwater Modeling

Advances in modeling technology are making a splash in enabling communities to develop targeted, economical flood mitigation measures.

Floodplain maps developed by the Federal Emergency Management Agency in the 1970s and ’80s were simple one-dimensional (1D) models that provided no spatial references. In the ’90s and 2000s, geographic information systems (GIS) were linked with stormwater models, enabling 1D model results to be mapped more accurately.

Today, by applying two-dimensional (2D) modeling with GIS, it is possible to simulate multiple directions in which the stormwater might move. Additionally, advances in mapping software with detailed lidar — light detection and ranging — elevation data have made the software more practical and cost-effective. Because of the increased detail and accuracy of the data, 2D floodplain models can be created more efficiently and provide more flood detail.

During heavy rainfall in big cities, drainage systems are sometimes overwhelmed, leaving them unable to direct all the water and allowing it to flow across the surface, causing localized flooding. Such events can cause damage to homes and businesses, leading to expensive repairs and replacements of equipment. In urban settings, 2D modeling of the surface flooding combined with models of the local pipe network can inform detailed maps of potential flooding and identify which areas are at higher risk. The 2D flood maps can then be used with other GIS data to determine which homes and businesses face significant flood risk and identify streets that may have safety issues caused by fast-moving water.

Numerous benefits are associated with 2D modeling:

• It significantly aids in avoiding unnecessary expenses by helping identify appropriate and strategic flood mitigation solutions.
• It provides the tools to simulate historical flooding events, increasing confidence in the model and building trust in future plans.
• It provides more accurate mapping, making it easier to see where flooding safety issues exist and anticipating issues related to nearby areas such as playgrounds or campgrounds.
• It supports improved communication with the public by providing accurate maps of historical and potential flood events.
• It can be used to simulate a range of design events, including two-, five-, 10-, 50- and 100-year events, to determine flood reduction benefits of various stormwater solutions.

In recent years, Burns & McDonnell has seen firsthand the benefits of utilizing 2D modeling in evaluating client watersheds to address flooding issues. For one client, the modeling enabled the city to refine planned improvements in a way that saved money by focusing on specific areas within the watershed that were subject to the greatest risk. For another, our ability to create accurate simulations of overbank flooding helped define solutions for when extreme rainfall events caused water to move out of defined channels in previously unexpected directions.

Every industry is leveraging technology to improve efficiency. Cities can utilize 2D modeling technology to develop and strengthen their storm-hardening measures. Flood risk management can be significantly improved through technological solutions such as GIS and real‐time remote monitoring systems. It has become easier than ever to adopt 2D models to create more realistic simulations of surface flooding within a city. This helps when evaluating that city’s underground pipe infrastructure to better assess its readiness for future extreme weather events. Models are only as good as the data that goes into them, and strong data can lay a foundation for sensible, strategic infrastructure investments.

Learn more about how we deploy modeling techniques to evaluate the hydraulic, financial and capital management processes that support your long-term planning efforts.