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Riverine Flooding or Localized Flooding: Which Type is Affecting your Community?

07.14.2021

DURATION 3 minute read

Many communities are experiencing flooding as extreme wet weather events become more common. The flooding caused by these events can be devastating, but there are steps communities can take to help address these issues, including the implementation of flood mitigation strategies.

There is a range of mitigation measures that can be used to help reduce community flooding. But, before community leaders can decide which strategy best addresses their community’s flooding needs, they need to determine what type of flooding is impacting the area.

There are two major types of flooding that impact Texas communities: Riverine and localized. But what distinguishes the two and which mitigation strategies best address them?

 

What is Riverine Flooding?

Riverine flooding occurs when excessive rainfall causes a river, stream, bayou, or other open channel conveyance feature to exceed its capacity. Generally, this type of flooding happens after high-intensity rainfall creates soil saturation and large runoff.

Damage from riverine flooding can be widespread since overflow can affect smaller rivers downstream – causing dams and dikes to break and flood nearby areas. The best way to address riverine flooding is through floodplain mitigation solutions that help water drain more efficiently. This type of mitigation receives flow from and provides additional volume for channel routing, which reduces flood levels.

What is Localized Flooding

What is Localized Flooding?

Localized flooding can occur for several reasons, including sheet flow patterns, ponding, and overwhelmed underground storm sewer systems.  Lately, Texas has experienced intense short-duration rainfall (for example high-intensity afternoon thunderstorms). This type of flooding generally occurs on a much smaller scale than riverine flooding and typically happens before rivers, streams, bayous and other conveyance systems have reached capacity.

Conveying stormwater into a detention basin that then outfalls into a stream or other natural sources is the best solution for addressing localized flooding and avoiding adverse impacts to downstream neighborhoods. This can be accomplished through multiple mitigation strategies, including a multi-use dry\wet detention basin.

A 1-D\2-D sheet flow analysis can be used to determine whether your area is experiencing localized flooding. This type of analysis mimics the natural flow of water and allows the user to analyze how floodwaters will move across terrain.

There are cases where an area experiences both localized and riverine flooding. When this is the case, a combination of detention and floodplain mitigation strategies can be used to address the issue.

Once it’s been determined what type of flooding is affecting your area, it’s time to find a detention and flood solution that meets the goals of your community! Our H&H team has been helping communities in Texas study and mitigate flooding for 45 years. Contact us to find out how our team can help! You can also check out some of our flood mitigation projects, including the Cypress Creek Watershed, the City of Houston Guidebook for Multi-Use Park Facilities, and the Buffalo Bayou Park.

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