Coastal challengesBay Area Coastal Flooding Triggers Region-Wide Commute Disruptions

Published 6 August 2020

Researchers have modeled how coastal flooding will impact commutes in the Bay Area over the next twenty years. Regions with sparse road networks will have some of the worst commute delays, regardless of their distances from the coast.

For decades, the low-lying neighborhoods along the San Francisco Bay have experienced coastal flooding and the subsequent traffic disruptions. But a new computational model by Stanford researchers reveals that, due to the nature of road networks in the region, commuters living outside the areas of flooding may experience some of the largest commute delays.

By integrating traffic models with regional flood maps, researchers have demonstrated how San Francisco Bay Area commute disruptions spread substantially inland, creating longer delays for communities with sparse road networks than for those in the areas of flooding. Climate change is exacerbating the situation by increasing the likelihood of extreme events like flooding. The research, published Aug. 5 in Science Advances, reveals that measuring road network density may be more important for understanding community resilience to flood-related commute delays than actual flood exposure.

“In disaster science, we usually say the hazard is the elephant in the room and the other things are details, but this study says the elephant in the room is really the existing structure, the existing vulnerability,” said senior author Jenny Suckale, an assistant professor of geophysics at Stanford University’s School of Earth, Energy & Environmental Sciences (Stanford Earth). “In this case, it’s the sparsity of the road network.”

The study is the first to quantify indirect impacts of Bay Area flooding, which are much more difficult to measure than direct impacts, such as the costs associated with flood damage to buildings, according to Suckale. Unraveling the indirect impacts of hazards has become an increasingly important directive from the Intergovernmental Panel on Climate Change (IPCC) in planning for future climate scenarios, including sea-level rise that will increase coastal flooding.

Likely coastal flooding scenarios

The researchers modeled how flooding will affect individual commuters over the next 20 years by integrating road network, census and traffic data from the 2010-20 period with regional flood maps from the Adapting to Rising Tides program, which were designed to aid sea-level rise adaptation planning efforts.

“We did not make assumptions about how population growth or commuters would change over the next two decades,” said lead author Indraneel Kasmalkar, an engineering PhD candidate affiliated with the Stanford Institute for Computational and Mathematical Engineering (ICME). “And if there are substantial changes to commute patterns, we can update our simulations accordingly.”