Rising seas could bring chronic flooding to Orange County

Imagine your street or even your house being flooded 26 times a year. Rising sea levels could make chronic flooding a reality for some Southern California communities in less than 50 years, according to a study released Wednesday from the Union of Concerned Scientists . 

Nationwide, more than 270 communities are at risk for the what the UCS defines as “chronic flooding” by 2060 given moderate sea level rise. The study was published in the journal Elementa .

Local communities at risk include parts of Long Beach, Seal Beach, Huntington Beach and Newport Beach. 

Study authors listed Huntington Beach among coastal communities that are particularly vulnerable: the city could see more than 10 percent of its land chronically flooded by 2100, according to the study. 

The above assessments assume an “intermediate” scenario, where carbon emissions peak in the next few decades, sea level rises about 4 feet globally and polar ice melts at a moderate but increasing rate. The study also looked at a “low” scenario, where global warming is limited to less than 2 degrees Celsius, in line with the major goal of the Paris climate agreement, and sea level rises less than 2 feet by 2100, and a “high” scenario, where emissions continue to rise and sea level rises 6.5 feet.

Under the low sea level rise scenario, between 200 and 400 communities nationwide could be spared chronic inundation, according to the study, including the north Orange County coast. 

Under the high sea level rise scenario, about a quarter of Huntington Beach’s territory could be subject to chronic flooding. 

Climate scientist Kristy Dahl, who co-authored the report, said the study is meant to "give communities a tool to understand how long they have before this frequent extensive flooding becomes a real problem and forces difficult decisions.”

Huntington Beach has done a detailed analysis of which parts of town are most at risk as sea level rises, and the city released a draft Coastal Resiliency Program last year. But it likely won’t adopt a plan to address those risks until it updates its local coastal program — a development guidebook that must be certified by the California Coastal Commission —which is several years away, according to Huntington Beach planning manager Jennifer Villasenor. 

Some other OC towns are further along. Newport Beach recently worked with the California Coastal Commission to update its coastal development program to plan for sea level rise . Among other measures, future development in the city’s coastal areas that are considered hazardous will have to waive the right to protection if rising seas threaten damage.

Check out the UCS’s interactive map of projected chronic inundation due to sea level rise.