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Likely peak assumes average runoff and that the lake can barely drain once it tops pool. When False River floods, the downstream channel (Bayou Grosse Tete) is high too — so the parish’s plan is to close the gates to keep that water from backflowing into the lake, and even open they couldn’t push the lake out against a higher downstream. That’s the parish’s written operating rule plus basic hydraulics, so above pool we assume little drainage until the downstream falls. Likely worst case stacks the three things that can go wrong at once: the rain comes in heavier than forecast, the ground is already soaked, and the gates can’t open to help. (For the rain, “likely” is the official NWS forecast; the worst case widens it by the spread across a multi‑model ensemble — dozens of model runs — so when the models disagree, as in a tropical setup, the worst case grows on its own.) It’s the conservative number to plan around if you have anything to protect near the water — a camp, a house, a dock, a boat. Peaks are the Corps gauge; the parish reading runs 0.5 ft higher.
Before you trust a number here
This tool is for general information only. For real decisions, always rely on the National Weather Service, Pointe Coupee Parish emergency officials, and your own eyes on the water.
I built this calculator to help me decide when it’s prudent to pull my boat off the lift. I use it myself, but I make no guarantee of its accuracy. Everything below — the assumptions, the data, and the math — is laid out so you can judge it for yourself.
The last 7 days
River level over the past week (Corps gauge). The dashed line is normal pool — 15.5 ft on this Corps gauge, which the parish gauge reads as 16 ft.
How much water False River is holding
At normal pool the lake is ~3,060 acres and ~22 billion gallons (avg depth 22 ft, per the USGS survey, WRI 99-4193). As it rises past the banks it spreads out — so each extra inch of rain raises it a little less. That built-in brake is why the lake rarely runs away, and it’s baked into every estimate here.
About False River’s drainage
False River is a cutoff oxbow — it has no natural river running through it, so its level is held by a couple of man-made outlets on the south end. There’s no big overflow “spillway”; the level is managed mostly by gates.
The Lighthouse Canal structure (the gates)
The main control is a gated structure at the Lighthouse Canal on the south end, on LA Hwy 1: three sluice gates over three 8×8 ft box culverts, capable of roughly 1,400 cubic feet per second — about 80% of the lake’s drainage. Its risers hold the lake at its normal pool of 16 ft on the parish gauge (15.5 ft on the Corps gauge this site is built on); when the lake rises above that, the gates are opened to let water out, and they’re opened wide for the periodic drawdowns. Water leaving here flows into the False River–Bayou Grosse Tete Canal and on into Bayou Grosse Tete, south of the lake.
Bayou Sère (the back-up outlet)
A second, passive outlet — no gates — that only really kicks in once the lake is up around 16.5 ft. It carries the remaining ~20%. In big storms it can briefly run backwards, pushing water back into the lake when the water downstream is higher than the lake — one reason a flood can be hard to drain.
Who runs it
The gates are operated by the False River Stage Control Committee — the Pointe Coupee Parish President, the Director of Administration, and the Director of Public Works — at the Parish President’s direction, with guidance available from the Louisiana Department of Wildlife & Fisheries and the Department of Natural Resources. (The separate multi-foot drawdowns every couple of years over fall and winter are a fisheries- and water-quality tool, not flood control.) The official gauge they operate to is at Satterfield’s Landing / Morrison Parkway.
Before a storm: the pre-storm drawdown
When heavy rain is forecast, the committee opens the gates ahead of time to draw the lake below pool so it has room to take the runoff. The parish’s published plan ties the target to the 7-day rainfall forecast — roughly: under 1″ forecast, hold pool; 3–6″, draw down to about 15 ft; over 9″, down to about 13.9 ft (all on the parish gauge). Their own rule of thumb is that 1 inch of rain raises the lake about 5 inches. But there’s a hard limit: the gates lower the lake only ~0.1 ft per day each — about 2 ft over a full week — so a fast tropical setup can outrun the head start. This is also why a level on this page can drop in the days before a storm, not just rise after one.
Why rain still floods it
Runoff from the ~56‑square‑mile watershed drains into the lake through gravity canals (M‑2 / Patin Dyke Slough on the north end, M‑1 / Discharge Bayou on the south). In a heavy storm, far more water pours in than 1,400 cfs of gates can let out — so the lake rises until the rain stops and the outlets slowly catch up. Worse, the parish’s own plan says that when the downstream channel backs up and tries to push water toward the lake, the gates are closed until that backflow subsides — so during the peak of a regional flood the lake genuinely can’t drain. That mismatch, and that gate-closure, are exactly what this tool’s “likely peak” assumes.
Sources: Pointe Coupee Parish Lake Level Management Plan (2019); 2012 USACE/LDWF False River Interim Feasibility Report; USGS WRI 99-4193; LDWF drawdown notices.
The record so far
Daily lake level since 2018 (weekly average). The dashed lines are normal pool (15.5 ft Corps / 16 ft parish) and the level the parish closes the river to boats (17.5 ft Corps / 18 ft parish).
Highest river levels (in the recent gauge record)
What’s behind the numbers
Real effort went into making this as accurate as a free tool can be — it’s a physics model of the lake’s water balance (rain in, runoff in, drainage out), calibrated against years of real gauge data and ground-truthed against the 2016 flood. It accounts for evaporation, the lake spreading over its banks, the drainage canals’ limited capacity, and the downstream tailwater that can stall the outlets.
- Lake level: USACE Rivergages station 52330 (“False River at New Roads”), daily back to October 2018 plus the hourly nowcast — the Corps/NGVD datum everything here is built on.
- Downstream tailwater: USGS 07381427, Bayou Grosse Tete — tells us when the outlets are backing up.
- Rainfall, past: Daymet 1 km daily, averaged over the False River watershed, with Open-Meteo filling the most recent days.
- Rainfall, forecast: the National Weather Service (api.weather.gov) gridpoint QPF is the likely amount; the worst case widens it by the spread across a multi‑model ensemble (the GFS + ICON ensembles, ~70 runs) via Open‑Meteo.
- Lake shape & capacity: USGS survey WRI 99-4193 (3,060 acres, 67,300 acre-ft, 22 ft mean depth at pool) plus a USGS 3DEP LiDAR DEM for how the water spreads above the banks.
- How the lake is operated: the Pointe Coupee Parish Lake Level Management Plan (2019) — gate operation, the pre-storm drawdown rule curve, normal pool, and the boat-closure level — plus the 2012 USACE/LDWF False River Interim Feasibility Report for the outlets, gate capacity, and watershed.
A note on datums: the Parish gauge reads exactly 6 inches higher than the Corps gauge — confirmed to the hundredth of a foot (on 18 June 2026 the parish’s 17.48 ft was the Corps gauge’s 16.98 ft). It’s a difference in where each gauge’s “zero” sits, not two different sea levels. This site is built on the Corps gauge and adds 0.5 ft to show the parish number, so normal pool is 15.5 ft here / 16 ft parish, and the river closes to boats at 17.5 ft here / 18 ft parish. Both are shown so they match whichever you’re used to hearing.
Get a heads-up by email
Optional alerts when False River is forecast to rise toward flood levels. No account, no spam — you’ll get one email to confirm, and you can stop anytime.