Delta Levees & the 2004 Jones Tract Flood in San Joaquin County

The 2004 Upper Jones Tract levee failure

In June 2004, a levee protecting the Upper Jones Tract -- a reclaimed island of farmland in the Delta near Stockton, in San Joaquin County -- failed, sending water rushing in and flooding roughly 12,000 acres of agricultural land. The break happened without an obvious storm event forcing it, illustrating a real vulnerability of Delta levees: many were built decades ago on peat soil that has continued to subside, and can fail from age, seepage, or structural weakness rather than only from an extreme flood event. Evacuations followed, and repairing the breach and pumping the island dry took weeks and cost tens of millions of dollars.

This event is one of the most concrete, well-documented illustrations available of why Delta land in San Joaquin County carries a different kind of flood risk than ordinary floodplain property elsewhere in the county or the state -- the risk is tied to the age and condition of a specific levee segment and reclamation district, not simply to elevation relative to a modeled flood event.

The statutory Delta framework still applies here

San Joaquin County's western portion falls within California's legally defined Sacramento-San Joaquin Delta, established by the Delta Protection Act (1959, expanded 1992) and further shaped by the Sacramento-San Joaquin Delta Reform Act of 2009, which created the Delta Stewardship Council and its region-wide Delta Plan. As in Sacramento County's own Delta portion, land here can fall within a statutorily defined primary or secondary zone, with the Delta Protection Commission holding a review role over land-use decisions within it, on top of ordinary San Joaquin County zoning.

Local reclamation districts -- special districts, often more than a century old, funded by assessments on the land they protect -- remain responsible for maintaining the levees. For any specific western-county parcel, confirm the responsible reclamation district, ask directly about that levee segment's current condition and any post-2004 improvement work, and check the parcel's primary/secondary Delta zone status with the Delta Protection Commission.

What to verify before relying on this

This page describes durable, historical facts about a documented 2004 disaster and the long-standing statutory Delta framework -- it does not describe current levee condition, current FEMA flood-zone mapping, or any specific reclamation district's current assessment rate, none of which were verified this pass. Confirm current flood-zone designation directly through FEMA's Flood Map Service Center, and confirm levee condition and assessment obligations directly with the relevant reclamation district and San Joaquin County before relying on this page in a purchase decision.