The Sacramento-San Joaquin Delta's ability to handle severe flooding is threatened by decades of sediment buildup in channels that haven't been dredged in over fifty years, according to an August 2026 analysis by Edward Ring, director of water and energy policy for the California Policy Center. The report warns that state and federal agencies have prioritized levee strengthening and habitat restoration while ignoring channel depth restoration through sediment removal, leaving the region vulnerable to a forecast "super El Nino" expected as early as 2027. Ring argues that without dredging, the delta's reduced flow capacity could trigger catastrophic flooding when heavy rains arrive.
The delta's geography creates unique flood dangers. All outgoing water must pass through a bottleneck north of Pittsburg that is barely one mile wide, separating over 1,000 square miles of delta with more than 1,000 linear miles of channels from the ocean. The worst flooding of the 20th century occurred in 1997, when days of continuous rain hit the Sierra slopes with the snow line unusually elevated at 10,000 feet, sending nearly all precipitation into the San Joaquin River and other tributaries. Reservoirs reached capacity and released water into spillways at rates far exceeding the flow capacity of downstream channels, overwhelming levees. Currently, the delta exports around four million acre feet of water annually to cities and farms through its engineered channels.
The report notes that the State Water Resources Control Board's August 2026 draft of the "Water Quality Control Plan for the San Francisco Bay/Sacramento-San Joaquin Delta Watershed" contains no mention of channel restoration through sediment removal. Ring identifies the Great Valley Farm Water Partnership as the only organization committed to sediment removal, having listed "silt removal in the south delta" first among seven essential actions for restoring the delta. According to the report, objections to sediment removal include concerns that advocating for dredging might undermine support for the delta tunnel project, worries that funding for silt removal could divert money from the tunnel or aqueduct repairs, and environmental concerns that dredging harms fish. Ring challenges the environmental objection by pointing out that "for over a century, from the mid 1800s through the mid 1970s, dredging was routinely performed throughout the delta, in every channel, and up every tributary. Through it all, salmon and smelt thrived."
The report argues that shallow channels created by sediment accumulation heat up, favoring introduced predators and invasive vegetation over native fish species that prefer deeper, cooler water. Ring suggests that historical dredging actually created habitat by maintaining deep, cool channels that allowed native fish to adapt and find refuge from predatory bass that thrive in warmer, shallower conditions. The conventional wisdom that sediment removal harms fish is called "well-intentioned but misguided" in the analysis. Ring contends that inadequate flow capacity has reached the level of a national emergency, which should unlock federal funding from sources unrelated to state water projects, addressing financial objections to dredging programs.
If levees fail due to reduced flow capacity from silt buildup, the report warns that flooding won't quickly escape but will instead inundate interior farms and cities. The resulting damage would reach into the billions, with raw sewage, fuels, and agricultural chemicals mixing into trapped flood water. When downstream runoff subsides, salt water from the ocean would flow through broken levees at high tide and flood the delta's many below-sea-level "islands," adding salinity contamination to the toxic mix. Water exports to aqueducts would cease entirely. Ring concludes that when the super El Nino brings a super flood—whether this year or within a few years—those who used their influence to block sediment removal "will have a great deal of explaining to do."