Navigating Los Angeles County’s flood-control system amid climate change

L.A.’s flood-control plan endured the epic storm, but it’s losing the fight with climate change.

Overview of the Situation:

Los Angeles County recently faced hammering rainfall, mud flows, and multiple state emergency declarations due to near-record precipitation. 

Despite these challenges, the county’s flood control system has managed to absorb the onslaught, thanks to extensive preparations and infrastructure measures.

Preparations and Infrastructure Measures:

Extensive preparations, including massive dredging of key debris basins and clearing of storm drains in vulnerable areas, have played a crucial role in managing the impacts of the intense rainfall. 

The county’s flood control system consists of 18 dams, 487 miles of flood-control channels, 3,300 miles of underground storm drain channels, and dozens of debris basins.

Challenges Posed by Climate Change:

However, concerns persist among local engineers and officials regarding the ability of the flood infrastructure, built on 20th-century hydrologic records, to withstand increasingly frequent extreme weather events driven by climate change. 

The system’s capacity may be tested, particularly when intense storms occur back-to-back without a break.

Sediment Accumulation in Reservoirs:

The recent storms have led to the accelerated accumulation of sediment in the county’s reservoirs, posing challenges for future flood management efforts. 

With over 15 million cubic yards of sediment currently in reservoirs, the task of removing and relocating it comes with a significant price tag of approximately $500 million.

Scientific Projections and Future Challenges:

Scientific studies, such as one conducted by UC Irvine, suggest that future epic storms could overwhelm the area’s principal waterways, including the Los Angeles River, Dominguez Channel, Compton Creek, and the San Gabriel River. 

As climate change continues to influence weather patterns, the county’s aging flood-control system faces increasing challenges in maintaining resilience against extreme events.