Before the Storms: Where Flood Protection Stands in Lodi, Stockton, and the North Delta

Weather
Written By Don Bradford
Before the Storms: Where Flood Protection Stands in Lodi, Stockton, and the North Delta

Before the Storms: Where Flood Protection Stands in Lodi, Stockton, and the North Delta

Lodi411 / LodiEye — Civic Infrastructure Brief — August 2026

Summary

NOAA now puts the odds of a very strong El Niño at greater than 90% for fall and winter 2026-27, and gives a 69% chance the October–December 2026 season sets a record for its three-month tropical Pacific temperature index dating back to 1950. The August 2026 Copernicus/ECMWF seasonal outlook calls wetter-than-average conditions likely across southern North America. A companion Lodi411 forecast report covers the atmospheric signal. This brief asks the next question: is the region's flood protection ready?

The answer sorts by clock. One project — the Tenmile Slough levee in west Stockton, described by San Joaquin County as the most critically deficient among those to be improved in the Central Valley system — is racing to finish by late October, weeks before the wet signal arrives. One asset — the Smith Canal Gate — is built, tested once in real weather, and about to face the busiest closure season of its short life. The rest of Stockton's $1.95 billion levee program runs on a design-and-construction schedule stretching into the late 2030s, and no comparable capital project exists on the Mokelumne corridor that runs past Lodi. For every reach that concrete cannot cover by December, this winter's protection is operational: reservoir flood space, district maintenance, levee patrols, and pre-positioned flood-fight supplies. Knowing which category each piece of the map falls into — and what to watch for each — is the point of this brief.

Three Clocks

Flood infrastructure only counts if it exists when the water comes. With the storm window opening in roughly December, every project in the region belongs to one of three categories: work that can finish before the storms, hardware that is built and must now operate correctly, and improvements that cannot arrive in time — where readiness has to substitute for construction. The table below sorts the major pieces.

Major flood-protection projects in the region, sorted by whether they will be in place for winter 2026-27
Project or system What it protects Status Timeline
Tenmile Slough levee (TS30L) West Stockton / Brookside Final construction season underway since early April 2026; soil-bentonite cutoff wall, reshaped levee, waterside erosion protection Target completion by end of October 2026 per SJAFCA; USACE describes completion by the end of 2026
Smith Canal Gate Central Stockton (Smith Tract area) Complete; first weather-driven closure January 2026 during king tides Operational — facing its first El Niño winter
Remaining Lower San Joaquin River Project reaches North and central Stockton waterfront reaches; Fourteenmile Slough Phased design 2025–2030; construction of remaining phases 2028–2035 Overall project completion anticipated by 2037 (USACE); earlier documents describe 2039
Mossdale Tract project (RD 17 area) Lathrop, Manteca, south Stockton — 22,400 acres Final Environmental Impact Report certified; project cost $473 million Not yet in construction
Mokelumne corridor Lodi, Woodbridge, Thornton, and the rural districts between No comparable capital project; protection is operational — reservoir flood space, district maintenance, patrols Ongoing operations

The Race to Late October: Tenmile Slough

The first constructed reach of the Lower San Joaquin River Project sits directly behind homes in Brookside, on a levee segment San Joaquin County describes as the most critically deficient among those to be improved — a levee SJAFCA's own leadership has described as not structurally stable at its core. The fix is substantial: a soil-bentonite cutoff wall driven to a maximum depth of about 50 feet, at an average design depth near 21 feet, to block seepage under the levee, along with rebuilt geometry and waterside erosion protection along approximately 1.1 miles. The U.S. Army Corps of Engineers puts the population protected by the eventual full system at an estimated 264,000 residents of north and central Stockton. The work was planned as two construction seasons — 2025 and 2026 — with the levee restored before each wet season.

The final season is going according to that plan. Heavy civil construction resumed in early April 2026, and on August 20 SJAFCA's executive director, Darren Suen, told Stocktonia the goal is to finish by the end of October, right around the start of storm season; a Corps aerial update posted August 17 with footage from July 7 describes completion "by the end of 2026" and shows the cutoff wall going in, the levee being reshaped, and waterside erosion protection being placed — independent visual evidence the reach is on pace. Suen also cautioned that a strong El Niño "doesn't necessarily mean San Joaquin County will be hit hard," noting past events "socked some regions while others remained relatively dry" over the course of a season. As of mid-August, the most time-critical project in the region is tracking to finish in almost the only year it could be tested immediately — and west Stockton would enter this winter with the strongest protection that stretch of levee has ever had.

Built, and About to Be Tested: The Smith Canal Gate

The gate across the mouth of Smith Canal is the region's newest flood asset, and January 2026 gave it a live rehearsal: its first weather-driven closure, triggered when water levels reached 8 feet during a king-tide event with rain in the forecast. That trigger combination is exactly what this winter multiplies. El Niño elevates regional sea levels; the California King Tides Project has published the season's headline dates as November 24–26 and December 23–25, 2026, and January 21–22, 2027; and the ECMWF seasonal outlook loads the rainfall side. A gate that closed once in its first year should expect to close repeatedly in its second. The readiness questions are operational, not structural: closure-decision protocols, staffing through the holidays, actuator and seal maintenance — and, above all, the interior drainage that takes over when the gate is shut. Which pump stations serve the area behind a closed gate, and who inspects them, is a public-record question that the Delta Stewardship Council's Smith Canal Gate operations attachment is expected to answer; on the public web, only the Wisconsin Pump Station, upgraded recently by Reclamation District 1614, is clearly documented as part of the local pump network. The gate's protection is only as good as the pumps behind it.

The insurance wrinkle: FEMA's revised flood map for the Smith Tract area took effect February 9, 2026, ending the mandatory flood-insurance requirement for property owners behind the gate. The remapping reflects the protection the gate provides — and it means thousands of central Stockton households gained the option to drop coverage in the exact year the region faces its highest-probability flood forecast in decades. SJAFCA's own notice adds that a lender may continue to require the coverage as a condition of the loan. Residual risk behind any gate or levee is never zero. Voluntary retention of flood insurance, at the lower preferred-risk rates a favorable map allows, is worth a conversation with an agent before the season starts.

The Decade Still to Come

The Lower San Joaquin River Project's full scope covers 23 miles of levee improvements plus two closure structures — Smith Canal, now built, and Fourteenmile Slough, still ahead. USACE's placemat lists design of the remaining phases at 2025–2030 and construction at 2028–2035, with overall project completion anticipated by 2037; earlier project documents used 2039, and both dates remain in circulation. South of the city, the Mossdale Tract project would fix levees in place along the San Joaquin River and French Camp Slough for 22,400 acres across Lathrop, Manteca, south Stockton and unincorporated county. The area's levees do not provide the 200-year flood protection state law requires for urban areas; Corps officials have described these cities as having the lowest level of flood protection among major U.S. river cities. The Final Environmental Impact Report is certified and the project carries a $473 million price tag, but construction has not begun.

None of that concrete arrives this winter. For the unimproved reaches, the honest description of this season's protection is: 1960s-era levees, district maintenance, patrol plans, monitoring, and the state's pre-positioned flood-fight stockpiles — more than 4.3 million sandbags, 55,000 super sacks, and 209 flood-fight material containers staged at 68 locations. That is not nothing; it is the same toolkit that held most of the system together in 1997 and 2017. But it is a fight-the-flood posture, not a keep-the-flood-out posture, and residents behind unimproved reaches should know which one they have.

The Mokelumne Corridor: What Actually Protects Lodi

Lodi's flood protection is not a levee program. It is a pair of reservoirs, an irrigation dam, and the rural reclamation districts downstream — a system that works through operations rather than construction, which makes it both older and, in a strange way, more adaptable than anything on the San Joaquin side.

The machinery starts 30 miles upstream. Pardee Reservoir (about 204,000 acre-feet) collects the Mokelumne for EBMUD's East Bay customers; Camanche Reservoir directly below it (about 417,000 acre-feet) is the system's flood-control workhorse, regulating releases to the lower river. Under the 1962 agreement between EBMUD and the U.S. Army Corps of Engineers, the two reservoirs must carry a combined flood reservation that increases daily from zero on September 15 to 200,000 acre-feet by November 5, and holds that space through March 15. Up to 70,000 acre-feet of the reservation is transferable to PG&E's Salt Springs and Lower Bear reservoirs upstream. Camanche is a USACE Section 7 reservoir operated to the Corps Flood Control Diagram; EBMUD's own scoping filing lists a Camanche storage target of 290,000 to 310,000 acre-feet on November 5 and a Pardee objective of at least 170,000 acre-feet. The same manual caps what the river below can take: releases are restricted to the extent possible to 5,000 cubic feet per second, the flood-control limit for the lower Mokelumne channel. The 200,000 acre-feet is not a discretionary call; it is a requirement with a November 5 deadline. What is discretionary is the release path to get there — and whether any of the space is shifted upstream. As of August 20, 2026, Camanche held 362,380 acre-feet and Pardee, on its most recent monthly reading, about 196,000 acre-feet; roughly 138,000 acre-feet of combined space remained to be created. Camanche's release rate on that date was 350 cfs. Meeting the diagram implies materially higher fall releases, and the daily storage and release figures at CDEC (Camanche), CDEC (Pardee), and the USACE Sacramento District Camanche release page are the numbers Lodi readers can watch.

The Mokelumne's Flood Machinery: Capacity, Space Required, and Where the Reservoirs Sat on August 20, 2026

Mokelumne system: capacity, recent storage, and required flood reservation
ItemAcre-feet
Pardee capacity203,795
Pardee storage (July 2026, estimated)196,320
Camanche capacity417,120
Camanche storage (August 20, 2026)362,380
Combined flood reservation required November 5–March 15 (up to)200,000

Reservoir capacities per EBMUD. Flood reservation per EBMUD's April 2026 FERC Scoping Document 2, describing the 1962 EBMUD–USACE agreement and the Camanche Flood Control Diagram; the reservation ramps from zero on September 15 to 200,000 acre-feet by November 5 and holds through March 15. Storage figures from CDEC daily and monthly data for stations CMN and PAR.

History gives the system's stress tests. Per EBMUD, Camanche's most recent maximum releases of 5,000 cfs occurred in 1997, when there was a slight spill, and again in 2006. Weeks of maximum releases around 5,000 cfs during the storms of February 2017 left the reservoir close to spilling. That episode also exercised the coordination playbook a repeat would require: EBMUD, San Joaquin County OES, and local agencies convened first responders and residents at the Woodbridge Fire District as the reservoir approached capacity. Both episodes ended without disaster on the main stem, and both are the planning template for a winter the models now expect to be wetter than either.

Below Camanche, the pieces are smaller but each matters. Woodbridge Irrigation District's dam at Lodi — the structure that forms Lodi Lake — sits directly in the release path, and the district is a year-round operator, not a summer one: its rights allow diversion of 300 cubic feet per second from February 1 through October 31, plus an additional 114.4 cfs from May 1 through August 31 and from November 1 through January 31, capped in aggregate at 414.4 cfs, serving roughly 63 square miles that include Woodbridge and Thornton. WID publishes dates rather than triggers; the district lowers Lodi Lake each winter for dam maintenance on an annual schedule (the 2026 cycle began January 30), and manages Lodi Lake level, WID diversion, and Joint Settlement Agreement flows below the dam with daily coordination with EBMUD. Under the JSA, flows released below the Woodbridge dam range from 100 to 325 cfs in normal and above-normal water years, stepping down in drier years. The city's own drainage rides on this system too — Lodi's storm runoff discharges to the Mokelumne, to the detention-basin parks, or to the WID canal, and under the 1993 City–WID agreement Lodi may discharge a maximum of 160 cfs in winter and 40 cfs in summer into the canal, which means the district's canal capacity is quietly part of the city's storm capacity. Downstream, the Thornton-area levees belong to Reclamation District 348, the New Hope Tract district, which maintains the levee system along the Mokelumne, South Mokelumne, and Beaver Slough with annual state cost-share funding through the Delta Levees Maintenance Subventions Program — its yearly maintenance filings are public record, and the Central Valley Flood Protection Board approves the funding each year. Thornton's exposure has state recognition of long standing: the companion Delta Levees Special Flood Control Projects Program was originally authorized in part specifically to address flooding at Thornton, New Hope, and Walnut Grove. These levees still protect farmland and a small town to a far lower standard than Stockton's urban system, and the 1997 breach remains the precedent — but the maintenance is funded, filed, and checkable, not ad hoc. And because state dam-safety rules adopted after Oroville require it, the inundation maps for a hypothetical Pardee or Camanche failure are public on the Division of Safety of Dams website — worth knowing they exist, with the standing caveat that EBMUD's dams are inspected under both state and federal jurisdiction and rated safe for continued operation.

Inside the City Limits: Lodi's Basins, Pumps, and What Actually Got Built

Lodi's drainage system has published design limits and a recent stress test on the record. Public Works Director Charles Swimley has described the storm drain system as designed to hold roughly 4.8 inches of water over a 48-hour period. The New Year's Eve 2022 storm delivered several inches on top of an already saturated December, with the detention-basin parks running well past comfortable capacity and streets functioning as their overflow; the city reported no homes flooded on the main event. At the March 28, 2023 Council Shirtsleeve Session, Senior Civil Engineer Sean Nathan and Public Works Director Charles Swimley presented eight candidate projects — Kofu Park, Vinewood Park, Shady Acres Pump Station, Pixley Park, Rose Gate Park, Rose Gate 2 Basin, DeBenedetti Park, and Vineyard Terrace — funded through a new capital improvement line, PWWW-25003 "Storm Drain System Improvements," carrying $400,000 per year across fiscal years 2024-25 through 2026-27, $1.2 million total, from Wastewater Capital Outlay.

Two items are built. The Kofu Park storm-drain improvement, accepted by Council January 15, 2025, installed a 24-inch high-density polyethylene culvert between the baseball diamond and skatepark so water passively flows into the skatepark area before the basin reaches capacity; the low bid was $94,700 by George Reed, Inc. against a $150,000 engineer's estimate, and the project completed on November 26, 2024 with no change orders. The Shady Acres Weir Replacement, accepted the same night, swapped a fixed concrete weir for a hinged aluminum weir that routes runoff through a trash-capture device before discharge to the WID canal and can be lowered for larger storms; ARB, Inc. built it for $37,541 against a $40,000 estimate.

The remaining projects are harder to find in the record. Pixley Park has no city funding, bid, or construction item in Legistar from October 2023 through August 2026 and does not appear in the capital-improvement forms for fiscal 2024-25, 2025-26, or 2026-27. Rose Gate and Rose Gate 2 appear only as subdivision map and improvement-agreement actions; the San Joaquin LAFCo municipal service review indicates that Rose Gate II is required to build a new detention basin and pump station as a developer obligation, not a city capital project. No Shady Acres pump-modification project appears in the record beyond the completed weir. The fiscal 2026-27 adopted capital forms contain no storm-drain basin page at all; the umbrella $400,000 line is the only visible funding vehicle carried into this winter. Whether specific successor projects to Pixley, Rose Gate, and the Shady Acres pump station are queued behind that line is a question the March 28, 2023 slide deck and the PWWW-25003 project files would answer, and a records request to the City Clerk is the direct path.

One structural point completes the picture. Roughly two billion dollars in flood investment is underway or planned on the San Joaquin side of the county, where the population and property concentrations are — a defensible allocation on the numbers. The Mokelumne side enters a potentially historic winter protected by operations, maintenance, and the lessons of 1997. That asymmetry is not a scandal; it is a choice, made over decades, that this winter will audit.

What Agencies Have Not Yet Said

Three items remain unstated in the public record, each with a single agency:

  • EBMUD: The 200,000 acre-feet of combined Pardee–Camanche flood space by November 5 is a requirement, not a plan. What EBMUD has not stated publicly is its posture for the actual drawdown — how much release, on what schedule, and whether any of the reservation shifts upstream to Salt Springs and Lower Bear. Nothing in EBMUD's press or news feeds through August 18, 2026 addresses winter 2026-27 or El Niño; the August 11 Board agenda listed a Dam Safety Program Annual Report but no flood-operations item. The next regular EBMUD Board meeting is September 8.
  • Woodbridge Irrigation District: WID has no published flow-threshold protocol. Operations are calendar-driven with daily EBMUD coordination, and the district's own notices explain that dates are "annual occurrences" that shift "depending on many variables." A written wet-season operating plan and the gate and flashboard criteria are not on WID's website; the request path is General Manager Keith Bussman.
  • San Joaquin County OES: As of August 21, 2026, OES has published no fall 2026 flood-preparedness update, no season outlook, no sandbag-site list, and no notice of a public flood-preparedness meeting. The most recent OES flood item is last season's December 19, 2025 flood watch; 2026 releases cover wildfire preparedness and housing recovery. The county's standing guidance remains that it does not provide sandbags. The San Joaquin County Flood Control and Water Conservation District cancelled both its July 15 and August 19, 2026 meetings; its last posted agenda is April 15, 2026, and its Flood and Dam Failure plan still dates to April 2023.

What Readers Can Track Themselves

Every item below is a direct link to a live agency page, dashboard, or agenda calendar. Bookmark the ones that matter for your address.

Reservoir storage and releases (the daily numbers)

El Niño and seasonal outlooks

Weather warnings and river forecasts

Stockton and San Joaquin projects (Tenmile, Smith Canal, LSJRP)

Lodi city documents and meeting agendas

San Joaquin County emergency and flood agencies

Maps: your address, your flood zone, your evacuation route

Reclamation districts and delta levee funding

Personal alerts

If you have questions, corrections, or local observations — particularly from the reclamation districts, Woodbridge, or Thornton — reach us at editor@lodi411.com.

LodiEye is the original civic-reporting and analysis arm of Lodi411.com, a citizen-run civic data and transparency platform serving Lodi, California and San Joaquin County. LodiEye gathers information of public interest, applies editorial judgment to public records, meetings, and data, and publishes original explanatory reporting for its readers — the work of a newsroom, and a representative of the news media as that term is defined under federal law. Our reporting emphasizes primary sources, public data, and full source transparency so readers can check every claim. LodiEye complements, and does not replace, the other outlets covering this region; for additional reporting on Lodi, San Joaquin County, and the broader region, we also encourage readers to consult the Lodi News-Sentinel, Stocktonia, The Sacramento Bee, CalMatters, and other established news organizations. Our full editorial standards and news-media-status statement is published at lodi411.com/editorial-standards.

This LodiEye civic infrastructure brief was produced using artificial intelligence tools under the direction and review of the founder. Lodi411 uses multiple AI platforms in its research and publication workflow, including Anthropic's Claude (primarily Opus and Sonnet models) and Perplexity AI across a variety of large language models offered by each. These tools were used in the following capacities:

Source Discovery: AI-assisted search and retrieval identified the project documentation and operational sources underlying this brief, including SJAFCA's Lower San Joaquin River Project and Smith Canal Gate materials, the U.S. Army Corps of Engineers Sacramento District project page and August 2026 aerial progress update, Stocktonia and CBS Sacramento reporting, EBMUD's reservoir and dam-safety documentation and April 2026 FERC Scoping Document 2 for the Lower Mokelumne River Project, CDEC daily and monthly reservoir data for Camanche and Pardee, USACE Sacramento District Camanche release data, Woodbridge Irrigation District organizational documentation and public notices, Reclamation District 348's annual levee-maintenance filings and the state Delta Levees Subventions program records, City of Lodi Legistar records for the Kofu Park and Shady Acres Weir Replacement projects and the FY2024-25 through FY2026-27 Capital Improvement Program forms, San Joaquin LAFCo's 2022 municipal service review, San Joaquin County Office of Emergency Services materials, NOAA Climate Prediction Center ENSO diagnostic discussions, and the Copernicus Climate Change Service seasonal-forecast highlights.

Credibility Validation: AI cross-referenced construction status and schedule claims against SJAFCA's public statements, the Corps' aerial update, and contemporaneous Stocktonia reporting; verified reservoir capacities, the 1962 flood-reservation framework, and the 5,000 cfs channel limit against EBMUD's FERC filing and EBMUD's own hearing documentation; confirmed the Woodbridge Irrigation District water-right structure against WID's own materials; confirmed the Kofu Park and Shady Acres Weir Replacement scopes, contract amounts, and completion dates against Lodi's Legistar staff reports; confirmed the RD 348 / Delta Subventions / CVFPB chain through state CEQA filings and program records; and distinguished agency-published facts from items that remain unstated by the responsible agency — presented in this brief as what agencies have not yet said, not as findings.

Analysis and Synthesis: Claude Opus and Sonnet assisted in organizing the region's projects into the three-clock framework (complete before the storms, operate correctly, readiness substitutes for construction), connecting the FEMA Smith Tract remapping to the flood-insurance decision facing affected households, and framing the investment asymmetry between the San Joaquin and Mokelumne corridors.

Presentation: Claude assisted in drafting, structuring, and formatting the report for clarity and readability, including the project status table and the Mokelumne storage chart.

Final Review: Multiple AI models reviewed the completed draft for factual consistency, source attribution accuracy, logical coherence, and balanced presentation. Throughout the process, the editor sets the report's goals, scope, and tone; creates and shapes draft content; reviews and edits the report; integrates independent fact checks; and reviews the AI cross-checks and validations. Multi-tool cross-checking across independent models and sources is the primary error-reduction mechanism.

Lodi411/LodiEye believes that transparency about how our research is produced — including our use of AI under human direction — strengthens trust with readers and the broader information ecosystem. Readers who spot an error are encouraged to write editor@lodi411.com so we can correct it.

References

Contact: editor@lodi411.com

Don Bradford
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