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Likely peak assumes average runoff and follows the gates: with the outlets open the lake drains by the height difference to the downstream — about two to three inches a day in the flood range, faster the bigger that gap — so once the rain eases the likely line falls with the lake. It holds the level up only when the downstream actually backs up against the gates and the parish closes them (a regional flood). Likely worst case stacks the three things that can go wrong at once — heavier rain than forecast, already-soaked ground, and gates that can’t open to help — so it’s the conservative number to plan around if you have something to protect near the water: a camp, a house, a dock, a boat. (For the rain, “likely” is the official NWS forecast; the worst case widens it by the spread across a multi‑model ensemble, so a tropical setup, where the models disagree, grows the worst case on its own.) 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.
5-day rainfall outlook
Extra context only — not part of the flood forecast above, which looks just 24–48 hours out (the range the model can be trusted at). The official NWS forecast is on top; below it, four independent global weather models each show their own next-5-days rain, so you can see where they agree — and, over time, judge which you trust. Daily totals in inches at the lake; bars share one scale so they’re comparable.
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, rated for about 1,400 cubic feet per second — the lake’s main outlet, carrying an estimated 80% of its drainage. But the gauge record tells the real story: in the flood range the lake actually draws down only about 2–3 inches a day — very roughly 250–400 cfs through the gates, well short of that rated maximum. The downstream Bayou Grosse Tete usually sits high enough to limit the height difference the gates drain against, so the model follows that live head, not the design number. In a big regional flood that canal can rise above the lake and try to push back through the gates — the backflow the parish watches for, and its cue to close them. The 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); above that the gates are opened to let water out, and 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 about a foot above pool (16.5 ft Corps). It carries the remaining ~20%. In big storms it can briefly run backwards, pushing water back into the lake when its own downstream is higher than the lake — one reason a flood can be hard to drain. Being ungated, there’s nothing to close when it does; the lake just has to wait for that downstream to fall.
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 the gates can let out — so the lake rises until the rain stops and the outlets catch up. The gates only drain when the downstream sits lower than the lake, which it usually does, so once the rain eases the lake draws itself down — roughly two to three inches a day in the flood range, faster the bigger the gap. While runoff is still arriving the net drop is smaller, which is why a level can ease only an inch a day even with the gates open. The exception is the peak of a regional flood, when Bayou Grosse Tete rises toward the lake’s own level and there’s no height difference left to drain against; the parish’s plan is to close the gates only if the downstream actually starts flowing backward into the lake (“should backflow occur … the gates shall be closed until the backflow subsides”). So the tool’s likely line drains the lake by that live height difference and eases off as the gap closes — holding the level up only once the downstream has backed up against the gates. The worst case always assumes the gates can’t help at all.
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)
How the estimate is figured
There’s no crystal ball here — just a water budget. Every estimate starts from the live Corps gauge, so the model never guesses where the lake is right now; it reads it. From there it adds up what goes into the lake and what leaves it over the next day or two:
- Rain on the lake goes in almost gallon-for-gallon — 3,000+ acres of open water catches a lot.
- Runoff from the watershed follows the watershed’s own engineering method (the NRCS curve number from the parish’s 2018 study): a light rain mostly soaks in, while a big storm sheds a much larger share — the way heavy clay ground behaves. Wet ground (the “ground saturation” slider) shifts that up, and the runoff arrives over the following couple of days as it travels down the M-1/M-2 canals, not all on the day it rains.
- Drainage out — the gates plus the Bayou Sère overflow — works on the height difference between the lake and the downstream Bayou Grosse Tete, read from its live gauge: the bigger the drop, the faster the lake drains (roughly two to three inches a day with the gates open). In a regional flood the downstream rises faster than the lake, that height difference collapses, and the parish closes the gates against backflow — so drainage chokes off right when the rain is heaviest, then recovers as the downstream falls. The likely line follows that live difference; the worst case assumes the gates can’t help at all.
- The lake spreading over its banks is read from a LiDAR survey: past the banks each extra inch of water spreads wider, so it raises the level less — the built-in brake that keeps floods here from running away.
- Slow losses — mainly evaporation, a couple tenths of an inch a day — come out too; small next to a storm, but part of why a level eases down through a dry stretch.
Two numbers come out of that. The likely line uses the watershed’s central runoff; the worst case stacks three bad things at once — heavier rain than forecast, already-soaked ground, and gates that can’t help. Neither is a single confident prediction; together they’re a range to plan inside.
How well it holds up
A model is only worth its track record, so I tested this one against what the lake actually did rather than trusting the math on faith:
- Replaying the rises in the record. Fed the rain that actually fell and the level it started from, the predicted peak missed the real one by about 0.3 ft (≈ 2%) in recent years. (With the rain known — so it measures the model’s grasp of the lake itself, not the forecast.)
- The 2016 flood — the benchmark, when the lake reached roughly 22 ft Corps on about 18″ of rain. The model lands there from the lake’s measured shape and outflow plus a limit on how fast the canals deliver runoff — and that limit comes out close to the most water the lake has ever taken in on a single day, so it isn’t just bent to fit 2016.
- Where it’s weakest is the big floods. They’re the hardest to call — the events where the rainfall itself is most uncertain — so the likely number can still run a little low. That’s exactly why a worst-case band sits above it, and why that’s the one to plan around.
- Following the lake back down. Replaying the drawdown after every past flood, the likely line now tracks the falling lake to within about 0.3 ft — it used to hold the lake near flood stage too long when the gates were actually open and draining. See the numbers ↗
What it can’t do: the biggest source of error is the rainfall itself — even past rain is only estimated, and two good datasets can disagree by nearly 2×; a forecast is looser still. Drainage now follows the live height difference to Bayou Grosse Tete and cross-checks the parish’s posted gate status, but neither reading is always current, so when they’re stale or unknown it stays conservative above pool. And above roughly 17.5 ft the lake is in territory the gauge has touched only briefly a handful of times — too rarely to pin down by measurement — so up there it leans on a LiDAR survey of the land and the highest numbers are rough upper bounds, not precise figures. That’s why every estimate here is a range, and why the worst case is the one to plan around.
What’s behind the numbers
It all runs on free, public data — no paid feeds. Here’s exactly what goes into it:
- 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
No account, no spam — one email to confirm, unsubscribe anytime. You’ll get an email when False River:
- is forecast to top 16 ft (6″ over pool) within 48 hours
- actually crosses 16 ft
- reaches 17.5 ft (18 ft parish) — when boat traffic stops
At most three emails per rise; the set resets once the river drops back below 16 ft.