Where Lodi Floods First: Scenarios for the 2026–27 El Niño Winter

Lodi
Written By Don Bradford
Fewer Cattle, Costlier Beef: Twenty Years of the U.S. Beef Industry and What It Means in San Joaquin County

LodiEye · Flood readiness

Where Lodi Floods First: Scenarios for the 2026–27 El Niño Winter

An interactive map and preparedness report covering street flooding, the Mokelumne River, Delta levees, critical facilities, dams and saltwater intrusion

September 25, 2026

California entered fall under a statewide emergency proclamation and a forecast for one of the strongest El Niño events on record (NOAA outlook). That is not a prediction that Lodi will flood. The local preparedness questions center on storm drains in town, the Mokelumne River corridor through Woodbridge and Thornton, north-Delta levees, and access to the White Slough wastewater plant west of Interstate 5.

Governor Gavin Newsom proclaimed the emergency on September 21. The proclamation itself warns that “very strong El Niño events do not produce uniform statewide outcomes.” This report sets out what each flood scenario would look like around Lodi, which parts can be mapped from official data, which cannot, and what local agencies can finish before the storms arrive.

>90%NOAA chance of a very strong El Niño this fall and winter (CPC, Sept. 10)
75%Chance that October–December strength sets a record (CPC)
8 of 9Lodi critical facilities checked that sit in FEMA’s 0.2% Zone X, outside the 1% floodplain
Zone AEFEMA zone at the White Slough wastewater plant’s County parcel point
5,000 cfsHistorical release target in a 1972 USGS study, not a verified current safe-flow limit
5Bridges over water in the map area rated scour critical in the National Bridge Inventory
  • Scenario map
  • Report
  • Preparedness
  • Facilities & gauges
  • Bridges
  • Sources & data

Map data: San Joaquin County GIS (FEMA flood zones, hydrography, reclamation districts, city limits), Caltrans functional classification (2024), National Bridge Inventory (June 2025), CDEC station metadata. Retrieved Sept. 23, 2026. FEMA zones are simplified for web display; confirm any address at the FEMA Flood Map Service Center.

The short version

Central Lodi sits mostly outside the Federal Emergency Management Agency’s 1% annual-chance floodplain, the regulatory “100-year” zone FEMA calls the Special Flood Hazard Area (SFHA). Much of the city falls instead in the 0.2% annual-chance “500-year” shaded Zone X. That is lower regulatory risk, not no risk. Storm drains overflow, roads close and power fails without any river leaving its banks.

The heavier exposure lies west and north of town. The Mokelumne River runs through Woodbridge toward Thornton and the north Delta, where farm tracts behind reclamation-district levees sit below the water beside them. A levee failure there would behave nothing like street ponding in Lodi. Water keeps flowing into a sunken tract until the levels equalize.

Among city facilities, the White Slough Water Pollution Control Facility stands out. Its San Joaquin County parcel point, 12751 N. Thornton Road, falls inside FEMA Zone AE, a 1% floodplain with a published base flood elevation. Every other facility checked here, including the four fire stations, police headquarters, City Hall, Adventist Health Lodi Memorial and the surface water treatment plant, screens into the 0.2% Zone X.

What this report is not. It does not replace National Weather Service warnings, County evacuation orders, dam emergency action plans or a FEMA flood-insurance determination. For a specific property, use the FEMA Flood Map Service Center. For warnings and evacuation routes, use San Joaquin County’s flood protection page.

What the forecast says, and what it doesn’t

El Niño is a warming of the tropical Pacific that tilts winter odds toward a wetter storm track across California. NOAA’s Climate Prediction Center (CPC) put the chance of a very strong event this fall and winter above 90%, with a 75% chance that October–December strength exceeds anything in the record back to 1950, measured by the relative Niño index (RONI) reaching +2.5°C (CPC ENSO discussion, Sept. 10, 2026). The next discussion comes out October 8.

A seasonal probability of above-normal precipitation is not a flood forecast. It says nothing about when an atmospheric river (AR) arrives, where its moisture plume stalls or how warm it runs. Those details decide whether the Mokelumne rises.

NOAA regional outlook and local planning implications
Period NOAA signal (CPC, Sept. 17) What it means locally
Oct.–Dec. Wet tilt focused on the southern half of California Weaker early signal here. Early storms still wet soils, fill ditches and expose clogged drains.
Dec.–Feb. Wet odds reach 50–60% near the coast Plan for back-to-back atmospheric rivers, high reservoir inflow and sustained levee loading if storms materialize.
Jan.–Mar. Wet odds 50–60% near the coast Compound risk increases if earlier storms saturate ground and use reservoir flood space.
Feb.–Apr. Wet odds 50–60% near the coast Late storms can land on a deep Sierra snowpack and full reservoirs.
Mar.–May El Niño expected to weaken significantly Risk shifts to actual snowpack, warm spells and remaining reservoir space.

The coastal percentages are not a probability for Lodi or for local flooding. The local implications are planning judgments, not NOAA event forecasts. NOAA’s next ENSO discussion is October 8 and its next seasonal outlook is October 15, 2026 (ENSO discussion; seasonal discussion).

Atmospheric rivers drive most western flood losses. A Scripps Institution of Oceanography team found ARs caused more than 84% of flood damage in western states over 40 years, averaging $1.1 billion a year, and each step up the five-category AR intensity scale brought roughly ten times more damage (Scripps).

Single-event hazards

Intense rain over town

A slow thunderstorm or a stalled rain band can overwhelm storm drains and roadside ditches while the Mokelumne stays well within its banks. Expect flooded intersections, water at low doorsteps, stalled cars and blocked driveways. Leaves on inlets, construction sediment and pumps that lose power make it worse. So does a canal or river running too high for storm water to drain into it by gravity.

One strong atmospheric river

A strong AR can bring valley rain, foothill runoff and heavy inflow to Pardee and Camanche reservoirs at the same time. Duration matters as much as peak rainfall. Long loading soaks levee embankments and raises groundwater on the land side.

Wind-driven storm

Saturated soil loosens tree roots. Downed trees and poles block emergency routes and cut power to pumps, lift stations, traffic signals and radio sites. In the Delta, sustained wind drives waves against exposed levee faces.

Warm rain on snow

A warm AR with a high snow level rains on terrain that normally stores snow and can melt the existing pack. Inflow to the Mokelumne reservoirs rises fast, operators have less time to make room, and high flows continue after valley rain ends.

High reservoir releases

Releases create flood space and are not an emergency by themselves. The hazard comes when high releases overlap with local runoff, high Delta stages or a second storm. Camanche Dam provides up to 200,000 acre-feet of flood reservation, which can be shared with Pardee, and protects Lodi, Woodbridge, Thornton and about 69,000 acres downstream, according to the U.S. Army Corps of Engineers 1999 post-flood assessment. The same report said release changes are limited to 1,000 cubic feet per second (cfs) every two hours, and that channel conditions had cut nondamaging flows to about half the 5,000 cfs design capacity at that time.

Delta tides and wind setup

High tides and strong wind can raise Delta channel levels with little upstream runoff. Alone, that tends to cause local overtopping, erosion and seepage. Paired with high river outflow, it keeps the downstream end of the system high while upstream water keeps arriving.

A hidden levee defect

Levees can fail short of a record flood. Underseepage and sand boils, burrows, decayed roots, cracks, slope slides and erosion at the water-side toe all start small. A boil carrying soil particles signals internal erosion and needs an engineer immediately. Cal OES guidance for levee-maintaining agencies calls for patrols during high water and immediate reporting of structural concerns (Cal OES).

The Mokelumne River corridor

Below Camanche, the Mokelumne carries dam releases, local runoff and, near Thornton, backwater from the Cosumnes River. A 1972 U.S. Geological Survey study evaluated a planned 5,000-cfs release target and found that severe Cosumnes backwater could add 4 to 6 feet at Benson’s Ferry. It also identified overbank flooding in some reaches at 5,000 cfs, with conclusions contingent on no levee failures and no significant channel changes since January 1970 (USGS, 1972). These are historical study conditions, not a current safe-release threshold or an evacuation trigger.

The Benson’s Ferry gauge near Thornton is the number to watch. The California Data Exchange Center (CDEC), run by the state Department of Water Resources (DWR), lists flood stage there at 17.0 feet. The record is 21.69 feet, set January 3, 1997 (CDEC station BEN).

Thornton has flooded before. San Joaquin County records that “in 1986, Delta islands and the Town of Thornton were flooded following a levee break” (County floodplain brochure).

Mokelumne River at Benson’s Ferry: stage thresholds (feet)
Action 12.0 ft; minor flood 17.0 ft; moderate 19.0 ft; major 20.0 ft; record 21.69 ft (Jan. 3, 1997). Source: CDEC BEN. Live stage and forecast: California Nevada River Forecast Center.

Roads and bridges

Roads usually fail before the regional flood map fills in. Water erodes shoulders, softens pavement bases, undermines culverts and washes out bridge approaches while the bridge itself stands. Caltrans’ District 10 climate assessment, which covers San Joaquin County, found 100-year storm depths increasing across the district and concluded that Caltrans “must assume higher rainfall and associated flooding” (Caltrans D10 report).

Bridge risk comes from scour, the fast water that strips sediment from around piers and abutments, plus debris jams, approach washouts and repeated peaks that leave no time to inspect between storms.

The Federal Highway Administration’s National Bridge Inventory (NBI), current to June 2025, lists 321 bridges over waterways in the map area. Inspectors rated 5 as scour critical, meaning the foundation is judged unstable under a scour event, and 17 have unknown foundations that have not been evaluated for scour. Another 5 carry installed scour countermeasures. The five scour-critical structures are New Hope Road over Grizzley Slough, Escalon-Bellota Road over Mormon Slough, Elliott Road and Lincoln Way over Dry Creek, and Harney Lane over North Paddy Creek (NBI via Bureau of Transportation Statistics).

Two Mokelumne-area county bridges combine a poor rating with an unknown foundation: Franklin Boulevard over the Mokelumne River overflow, whose lowest component rating is 1 on the 0–9 NBI scale, and Walnut Grove Road over the Mokelumne River. NBI ratings reflect the inspection date shown in the Bridges tab. Repairs completed since then will not appear.

Bridges over water in the map area, by NBI scour rating
Stable, within footing 185; stable, above footing 109; unknown foundation 17; countermeasures installed 5; scour critical 5. Item 113 of the NBI. Condition: 145 good, 147 fair, 29 poor.

How storms stack up

The main danger is not one storm. It is a sequence that hits before rivers, drains, reservoirs and levees recover from the last one.

A. Saturation staircase

  1. An October or November storm wets valley and foothill soils.
  2. Moderate storms fill ditches, canals and shallow groundwater.
  3. A strong December or January AR hits ground that can no longer absorb.
  4. A second AR arrives before channels recede.

The likeliest route to widespread road flooding and levee seepage.

B. Reservoir squeeze

  1. Early storms push Mokelumne inflow up.
  2. Camanche absorbs the peaks, then releases to restore flood space.
  3. River stages stay high downstream.
  4. A warmer storm arrives with a high snow level.

The test is whether forecast inflow exceeds remaining flood space while the lower river is already carrying releases.

C. Back-to-back ARs

  1. The first AR floods streets and soaks levees.
  2. Wind cuts power and blocks patrol roads.
  3. Repairs start while water stays high.
  4. A second or third AR lands within days.

Seepage, slope failures, erosion and debris jams compound.

D. Rain-on-snow pulse

  1. Cold storms build a Sierra snowpack.
  2. Reservoir storage climbs.
  3. A subtropical AR raises snow levels.
  4. Rain and melt reach the reservoirs together while downstream tributaries run high.

The fastest watershed-wide escalation.

E. Breach during high water

  1. Sustained high stages cause seepage.
  2. A sand boil grows.
  3. Flooded roads or wind damage slow access.
  4. The land-side slope fails or the crest breaches.
  5. A sunken tract fills.

Deep, long-lasting flooding of farms, roads, pumps and utilities.

F. Breach and salinity

  1. One or more Delta levees fail.
  2. Sunken islands fill with enormous volumes of water.
  3. The inrush pulls water from downstream channels.
  4. River outflow later drops while breaches stay open.
  5. Saltier water moves deeper into the Delta.

The main flood-related path to saltwater intrusion.

DWR notes that some central and western Delta islands sit 20 feet below sea level, that “the deeper an island subsides, the greater the risk of levee failure,” and that “every Delta island has flooded at least once since farmers began reclamation in the late 1800s” (DWR).

The most dangerous chain

The worst credible weather-driven sequence runs like this: a wet fall; several December–January ARs that fill reservoirs and raise channels; a warm AR that rains high in the Sierra; Camanche inflow rising while releases and Delta stages are already high; wind outages that stop pumps and patrols; seepage or a breach on a north-Delta levee; farm tracts flooded with mixed river, drainage, wastewater and farm runoff; and, weeks later, falling outflow that lets tides pull salt through an open breach. Each link is physically plausible. The full chain is unlikely. That is why monitoring should track storm spacing, snow level, Camanche inflow and release, Delta stage, power status, road access and observed seepage rather than seasonal rainfall totals.

Saltwater and the Delta

Saltwater intrusion has three distinct causes, and only one ties directly to a wet winter.

Three paths for salt to move inland
Mechanism When Link to storms
Low-outflow intrusion Late summer, drought River releases too low to hold back tidal salt. Weakly tied to a wet winter.
Breach-driven intrusion During and after a levee failure A filling island draws water from surrounding channels and can pull the salt boundary inland.
Tide and wind setup King tides, strong wind Raises channel levels and salinity pressure, especially after runoff drops.

The 2004 Jones Tract failure shows how a single break plays out. On June 3, 2004, with no storm, a 450-foot breach opened on the Middle River levee and flooded 12,000 acres to an average depth of 15 feet, about 180,000 acre-feet of water. The State Water Project cut exports at the Banks Pumping Plant for six days, and salinity, measured as electrical conductivity (EC), exceeded standards for 13 days at Jersey Point and Emmaton in the western Delta. The breach closed June 30. Worse salinity was avoided partly because operators cut south Delta exports and raised Sacramento River releases (DWR Bulletin 132-05).

DWR warns that the rush of water onto flooded islands “could draw ocean water deep into the Delta, interrupting water diversions for months or years” (DWR). Winter storm outflow initially pushes salt west. The risk grows later, when freshwater peaks recede and breached islands stay open to the tides.

Farm contamination

Floodwater does not need salt to ruin a crop. Water crossing dairies, septic fields, roads, fuel tanks, chemical storage and wastewater sites picks up pathogens, nutrients, petroleum, pesticides and metals. The U.S. Food and Drug Administration (FDA) treats the edible portion of a crop that contacts floodwater as adulterated and says there is “no practical method of reconditioning” it for human food (FDA guidance).

  • Manure lagoon overflow into fields and canals.
  • Septic system and private-well inundation.
  • Wastewater bypass or lift-station failure.
  • Fertilizer, pesticide and fuel mobilization.
  • Sediment and debris on vineyards, orchards and row crops.
  • Salt left behind after a Delta breach drains.

Damage continues after water leaves: root disease from saturation, soil compaction, well disinfection and testing, sediment removal and waiting periods before replanting.

Where each hazard hits hardest

Relative local concern by area
Hazard Central Lodi Woodbridge / Mokelumne Thornton / north Delta Delta agriculture
Intense local rain High High High Moderate
Single atmospheric river Moderate–high High High High
Repeated atmospheric rivers High Very high Very high Very high
Rain on snow Moderate Very high High High
Release overlap Low–moderate Very high High Moderate–high
Levee breach Lower likelihood High consequence Very high consequence Very high consequence
Road and bridge damage Moderate High High High
Saltwater intrusion Low Low Moderate Very high if breaches occur
Farm contamination Moderate at edges High Very high Very high

Ratings are a LodiEye planning judgment built from the sources in this report. They are not an engineering risk assessment.

Levees: what the district map shows

San Joaquin County has more miles of levees than any other county in the nation (San Joaquin County). Reclamation districts, local agencies that maintain levees and drainage for specific tracts, carry that work tract by tract. The map’s district layer shows 23 of them, including RD 348 (New Hope) and RD 38 (Staten Island) along the Mokelumne.

A district boundary is an administrative line. It is not a levee alignment, a condition rating or a breach footprint. Levee condition has to come from inspection records: the Corps’ routine and periodic inspections, DWR annual inspections and each district engineer’s report. The Corps rates each levee segment Acceptable, Minimally Acceptable or Unacceptable. “Minimally Acceptable” means deficiencies need correcting but are not expected to keep the levee from performing in the next flood (USACE levee inspections). Levees must hold at least that rating to stay eligible for federal rehabilitation under Public Law 84-99.

The County’s flood history lists levee failures in 1980 (Middle River, about $32 million in damage), 1983 (more than 16,000 acres flooded), 1986 (Delta islands and Thornton) and the dry-weather Jones Tract break of 2004 (County floodplain brochure).

Dam failure

Dam failure is a low-probability, extreme-consequence scenario. The map does not draw a dam-failure flood area, because that footprint must come from the dam owner’s approved inundation map, not an estimate. California posts approved inundation maps through DWR’s Dam Breach Inundation Map Web Publisher. The Governor’s proclamation directs DWR’s Division of Safety of Dams to remind dam owners of their duties to inspect, operate, maintain and repair their dams under their emergency action plans (proclamation).

What the state emergency does

The September 21 proclamation is preparatory. It does not predict a flood in Lodi. Among its directives:

  • The Governor’s Office of Emergency Services (Cal OES) coordinates statewide preparation and works with DWR to pre-position personnel, equipment, supplies and commodities based on forecasts and local needs.
  • DWR procures, stages and replenishes flood-fight supplies, including sandbags, riprap, plastic sheeting and pumps.
  • State environmental and natural-resources agencies prioritize permits for levee repair, vegetation management, debris and sediment removal, bridge-scour protection and channel-capacity work, with a joint recommendation on further emergency suspensions due October 16, 2026.
  • Cal OES and DWR reach out to counties, cities and local agencies responsible for levees and flood-control facilities, which are to stock and stage their own flood-fight supplies.
  • State contracting rules are suspended as needed to buy emergency goods and services quickly.
  • Caltrans and the California State Transportation Agency must identify vulnerable highways, bridges, culverts and other transportation assets and send Cal OES a prioritized project list within 30 days of September 21. Caltrans must plan to pre-position traffic-control, road-closure, warning and snow-removal equipment (directives 10–11).
  • The California Military Department must identify National Guard personnel, equipment and capabilities available for emergency support if activated or tasked. This is readiness planning, not an announcement that Guard units have deployed to Lodi (directive 12).
  • California Volunteers and the California Conservation Corps prepare personnel for assistance within their training, missions and safety requirements (directives 13–14).
  • State agencies coordinate with critical-service providers on readiness and restoration of power, water, wastewater, telecommunications and transportation. Cal OES must expand accessible, multilingual preparedness communications (directives 15–16).

These are statewide assignments, not evidence that a particular Lodi project, stockpile or deployment is complete. Residents can enroll for text, phone or email notifications through San Joaquin County’s SJReady Alerts.

Twelve priorities before the storms

The test of readiness is whether Lodi can keep fire response, dispatch, hospital access, drinking water, wastewater treatment, electric service and public warning running through a multi-day compound event. The priorities below are sorted by deadline. Select a row for detail.

White Slough comes first

The wastewater plant is the one screened city facility inside a 1% floodplain. A parcel-level flood zone is only the start. Treatment plants hold switchgear, generators, chemical storage, laboratories, headworks, lift stations and outfalls at very different elevations. The City’s review should put the following on one georeferenced site plan:

  • FEMA zone limits and the effective base flood elevation.
  • Surveyed floor and critical-equipment elevations on the same vertical datum.
  • Electrical distribution, generators, fuel tanks and transfer switches.
  • Influent, effluent, bypass, lift-station and outfall structures.
  • Chemical storage, anchoring and secondary containment.
  • Primary and secondary access roads, gates and low road sections.
  • Existing berms, walls, deployable barriers, pumps and drainage paths.

Before the wet season: load-test generators, line up two separate fuel-delivery options, stage portable pumps and watertight connectors, and confirm bypass authority and sampling procedures. The City lists White Slough at 12751 N. Thornton Road (City of Lodi).

Routes, not just buildings

A fire station outside the floodplain still fails if its only route crosses a flooded underpass. The City and County should map primary, alternate and emergency-only routes for the four fire stations, police and dispatch, the hospital, both treatment plants, fuel sites, shelters and mutual-aid entry points. For each route, record the controlling low point, the responsible road agency, who can close it and how crews confirm it is passable. The County’s Flood and Dam Failure Hazard Annex expects incorporated cities to use local resources and mutual aid before requesting County support (County annex).

Levee records by segment

Condition changes from one tract to the next, so the record has to be built segment by segment. Request from each levee-maintaining agency the latest Corps inspection rating, DWR inspection sheets, the district engineer’s report, deficiency close-out records, the high-water patrol plan and trigger elevations, the flood-fight plan and material inventory, and any piezometer or settlement readings. A public deficiency register should list, for each observation, the district, segment, location, type, severity, dates, responsible party, interim action and repair status.

Four trigger levels

Patrols and flood-fight work should start from written triggers, not judgment made after trouble is visible. The County annex notes that elevated threat periods can require 24-hour patrols under local maintaining-agency plans (County annex).

Trigger matrix
Level Trigger examples Actions
1. Monitoring Significant storm in the 5–7 day outlook; soils trending wet; higher reservoir releases possible Daily coordination call; verify contacts; inspect pumps, generators and vehicles; confirm material access and vendors.
2. Readiness Flood watch; forecast river rise; repeated storms; drains already burdened Staff emergency operations center (EOC) planning roles; alert contractors and mutual aid; inspect known trouble spots; stage barricades and pumps; issue preparedness messages.
3. High water Flood warning; preset gauge stage reached, such as Benson’s Ferry action stage of 12 ft; reported seepage or boil; road flooding Begin continuous levee patrol where required; open field command; dispatch engineers; close unsafe roads; open staging sites; send targeted warnings.
4. Emergency Overtopping forecast; growing boil; slope movement; uncontrolled seepage; breach signs; loss of critical access Immediate life-safety warning and evacuation action; request County and DWR support; flood-fight only under qualified supervision; protect responder escape routes.

Flood-fight stockpiles

Cal OES offers a planning benchmark: about 5,000 sandbags, ten rolls of 20-by-100-foot, 10-mil plastic, 200 wooden stakes, 1,000 tie buttons, twine and hand tools for every five to six miles of levee, plus life jackets for everyone on the levee (Cal OES guide). Split caches across sites outside likely flood areas, with named 24-hour keyholders, current inventories, sand sources, loaders and delivery vehicles. DWR offers free flood-fight training to local agencies (DWR flood preparedness).

Power, warning and evacuation

Every critical facility needs an electrical continuity package: critical loads, generator capacity, realistic fuel burn, transfer-switch test dates and runtime without resupply. Fuel contracts should carry priority status, a second supplier and delivery terms for closed-road conditions.

Warnings should name the hazard and the zone, lead with the required action and run in English and Spanish at minimum. Pre-write messages for flood watches, street-flooding “turn around” notices, specific road closures, evacuation warnings and orders, shelter locations and water or wastewater service interruptions. The County directs residents to official alerts and NOAA Weather Radio at 162.55 MHz, and publishes evacuation and shelter maps (San Joaquin County).

Thornton and north-Delta evacuation plans need trigger points set before overtopping or breach, transportation for residents without cars, plans for farmworkers, care facilities and livestock, and shelters outside the same flood and outage footprint.

The first 30 days

30-day work plan
By day Deliverable Lead partners
7 Confirm facility locations, contacts, backup power and access routes Lodi Public Works, Fire, Police, Electric Utility, hospital
10 Request current Mokelumne and north-Delta levee inspection reports and deficiency logs County OES and Public Works, reclamation districts, DWR, USACE
14 Finish the White Slough site walk and elevation memo Lodi Public Works, consulting engineer, Electric Utility
14 Adopt the four-level trigger matrix and a daily situation-report template Lodi EOC, County OES, NWS and DWR liaisons
21 Inspect pumps, generators, barriers and flood-fight caches in person Public Works, Fire, reclamation districts
21 Drive and confirm primary and alternate critical routes Fire, Police, Public Works, Caltrans, County Roads
30 Run a tabletop exercise and publish a corrective-action tracker Lodi and County OES
30 Publish a public preparedness page with maps, alerts, routes and bilingual messages City public information officer, County OES, community partners

Critical facilities and monitoring stations

Each facility is placed on its County parcel or street-address point and screened against the FEMA flood zones. Search by name, function or zone, then select a row for detail and a map link.

Critical facilities

A parcel point shows which FEMA zone a site falls in. It does not show the elevation of pumps, switchgear or generators. White Slough’s parcel point lies in Zone AE; every other facility listed lies in 0.2% Zone X.

River gauges, reservoirs and salinity stations

Stage thresholds come from the California Data Exchange Center (CDEC) and the National Weather Service. Select an ID for current readings.

Bridges over water

These are the 321 bridges in the map area that cross a creek, slough, river or canal, from the National Bridge Inventory (NBI). The table starts with the lowest component ratings. Scour rating (NBI Item 113) describes how vulnerable the foundation is to erosion during high flow. “Scour critical” means the foundation is judged unstable for assessed flood conditions; “unknown foundation” means the foundation type has not been determined.

Source: National Bridge Inventory, Bureau of Transportation Statistics, June 20, 2025 edition. Ratings reflect each bridge’s listed inspection date; later repairs are not shown. Condition: Good, Fair or Poor from the lowest of deck, superstructure and substructure ratings on a 0–9 scale.

Watch conditions yourself

How the map sorts its data

Data classes
Class What it means Layers
Authoritative Published by the agency responsible for the record FEMA flood zones; NBI bridges; County hydrography
Administrative Jurisdiction lines, not hazard lines Reclamation districts; city limits; Caltrans road classification
Planning Locations checked for exposure; not operational status Critical facilities; scenario groupings
Monitoring Stations with live readings at the linked source CDEC gauges, reservoirs and salinity stations
Hypothetical Scenario narrative only; no footprint drawn Dam failure; levee breach; street ponding; salinity intrusion

What the map cannot show

  • Dam-failure inundation. No approved GIS footprint is included in this package. The County’s OES Dam Inundation download failed on September 23 and again on September 25, 2026. Use DWR’s inundation map publisher; a failed download does not mean approved maps do not exist.
  • Levee breach areas and condition. The package does not contain current, comparable, segment-level condition records for the Mokelumne and north-Delta districts.
  • Street ponding. No verified pluvial-depth model or recurring-flood location list was obtained for this package.
  • Road closures. Closures are live operational data. Check Caltrans QuickMap and County alerts.
  • Evacuation zones and travel times. These must come from County OES, not from FEMA or district polygons.
  • Facility elevations. Points show County parcel or address locations, not surveyed equipment elevations.
  • Salinity movement. EC stations show where to watch readings. No salinity model geometry is drawn.

FEMA maps describe regulatory probability zones, not the footprint of the next storm. Areas outside the SFHA can and do flood.

Terms used here

SFHA
Special Flood Hazard Area: FEMA’s 1% annual-chance floodplain (Zones A, AE, AH, AO).
Zone X (0.2%)
Shaded Zone X: the 0.2% annual-chance, or “500-year,” flood area.
Levee-reduced Zone X
Area FEMA maps with reduced risk because of an accredited levee. The levee can still fail or be overtopped.
Floodway
The river channel plus adjacent land that must stay open to carry the 1% flood.
AR
Atmospheric river: a long band of concentrated moisture that produces most heavy West Coast storms.
cfs
Cubic feet per second, the standard measure of river flow.
Acre-foot
Water covering one acre one foot deep, about 326,000 gallons.
EC
Electrical conductivity, the standard field measure of salinity.
RD
Reclamation district: a local agency that maintains levees and drainage for a tract.
NBI
National Bridge Inventory, the federal bridge inspection database.
Scour critical
NBI Item 113 code 3: a foundation judged unstable under assessed scour conditions.
CDEC / CNRFC
California Data Exchange Center (DWR) and the NOAA California Nevada River Forecast Center.
OES / EOC
Office of Emergency Services; emergency operations center.
PL 84-99
Federal law under which the Corps repairs eligible flood-damaged levees.

Sources

Forecast and proclamation sources checked September 25, 2026. Map layers retain their September 23 retrieval date and the older source editions identified below; the map is not a live incident feed.

Contact: editor@lodi411.com

Don Bradford
Next

Fewer Cattle, Costlier Beef: Twenty Years of the U.S. Beef Industry and What It Means in San Joaquin County