Buckland Plants

Reduce Flooding Risks in Urban Areas

Flooding is a common risk that affects homes in communities across Los Angeles County. It can occur in the form of heavy rains, a weather disaster or even a flash flood – events that are less frequent but can be more severe and impact a greater number of properties.

The risk of flooding is particularly significant for low-income communities in urban areas, where many residents live close to water, have a history of exposure and have limited resources to prepare and recover from extreme weather events. In addition to the physical damage caused by flooding, these events can interrupt essential services, including emergency response times, access to jobs and education, and transportation options.

But what if we could reduce the risk flooding risks LA of flooding to help people be more resilient? That’s what our new study suggests we can do.

A team of UC Irvine scientists has developed a high-resolution flood modeling platform that can assess risks every 10 feet in the city of Los Angeles. The new system, which was published today in Nature Sustainability, connects hazards from rainfall, stream flow and storm tides with demographic data such as population density, race and economic disadvantage.

Using the tool, the researchers found that hundreds of thousands of people in urban Los Angeles are at high risk for flooding from a 100-year event. The analysis also shows that black and Hispanic residents are disproportionately exposed to flood risks. The new model is an important step in a broader effort to better understand and address flooding risks in cities. Harrison Wollman, a spokesman for the mayor of Los Angeles, says city officials have held public information sessions on flood risks and have been working with FEMA and the Army Corps of Engineers to update flood hazard maps.

While FEMA directives require the mapping of fluvial (river) and coastal hazards, there’s a lack of attention to flooding from rainfall runoff. This is because rainfall hazards can be harder to identify and model than fluvial and coastal risks based on the large-scale hydraulic models used by government agencies.

The new UCI research, which relies on the powerful PRIMo computer modeling software, reveals that rainfall-related flood hazards in urban areas are up to 10-40 fold higher than suggested by federally defined flood zones. The authors say their findings reinforce previous nationwide studies that have shown that the underestimation of flood risks is more pronounced in urban settings than in rural ones.

The team says it’s important to focus on solutions that reduce the risks of flooding, which can be addressed through a combination of green infrastructure and resilience measures. The former is a series of natural systems that slow and direct water flows away from the most vulnerable places, while resilience measures are community-wide strategies to build resiliency and improve resiliency in the face of flooding and other climate risks. The researchers are continuing to work on other projects that include assessing how wildfires may affect the flooding risk in LA, as well as looking at the impact of nuisance floods (those smaller, less intense events that don’t get headlines but can still cause major damage). They hope their work will contribute to more informed decisions about how to protect homes and communities from climate change impacts.