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⤴Unusual rise — FloodRadar+Top 1% rise rate for this gauge.
Height for "Above a height"
Drag the line on the chart, or type a value:mASD
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You'll be notified when this gauge is rising more than 0.10 m/hr — a sign of rapidly increasing water levels.
You'll be notified when a new storm-overflow (sewage) discharge starts within ~3 km of this gauge, based on the water companies' near-real-time feeds.
Get notified when recent rainfall near this gauge crosses its learnt rise trigger — an early "watch"
signal, typically hours before a rise. Experimental; not an official flood warning.
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Not an emergency service — if in danger call 999. Alerts rely on
EA/SEPA/NRW data and are best-efforts. Terms
Current Level
0.031 mASD
▬ Steady
24h Max
0.036 mASD
24h Min
0.031 mASD
Typical Range
0.02 - 1.55
mASD
Highest Recorded
0.69 mASD
1 Feb 2014
Since Nov 2012
Current level is 4% of this
🚽Sewage overflows nearby
Recent Water Levels
🌍 floodradar.co.uk
1 day
EA forecast (official)
Prediction V2
Prediction Eris
Nimbus beta
Experimental model fusing soil moisture, river flow, groundwater and catchment
character. The shaded band is its 10–90% range, widened so that about 80% of recent outcomes fall inside it.
Under evaluation — not yet promoted, so treat as a second opinion.
River Flow
90 days
Daily mean discharge (m³/s) with the daily min–max band, from the EA Hydrology API. Flow is the volume of water passing the gauge — often a more direct flood signal than level.
Flow Data: Daily mean flow (m³/s) to 9 Oct (2 days behind — the EA publishes each day's mean a day or two after it ends; unchecked, provisional)via EA Hydrology
Storm overflows whose water reaches this gauge on the mapped river network, nearest first by distance along the river. The status is each water company's monitor: it says whether an overflow is discharging, not how much or what it contains.
5 storm overflows are traced upstream of this gauge, the nearest 7.4 km away along the river. 0 report discharging now, 4 report not discharging, and for 1 the monitor is offline or has not reported, so their status is not known.
Thames Water · into Tidal River Thames · 5.6 km away in a straight line · discharges to the sea, an estuary or tidal water
0 spills · 0 hours in 2025
Not discharging now
5 other overflows within 6 km are downstream of this gauge or on another branch of the river network, so they are not listed.
These are the water companies' monitor statuses; a spill does not by itself explain a change in the gauge level. River connections and distances are traced on OS Open Rivers (edition 2026-04), which leaves out many small channels. Explore the sewage map →
Warnings apply to a whole flood area, not necessarily this exact spot. Years before 2006 aren't covered by the EA's historic record.
See also the Twickenham flood history.
Flood areas linked to this gauge
Flood warnings and alerts are issued for whole areas. These are the 9 areas linked to this gauge, nearest first.
🌊 Urban & flashyHeavily built-up — rain runs off hard surfaces fast, so levels can spike within hours of heavy rain.
Your catchment is all the land that drains rainfall into the river above this gauge. Its character — how
steep, wet, wooded, urban or chalky that land is — decides how fast rain here turns into a rising river. A steep, bare or clay
catchment is “flashy” (rises and falls quickly, floods easily); a flat, chalk or well-wooded one is
slow and steady. The tiles below put numbers to that; the flow-duration curve reads left-to-right
from the river’s typical high flows (Q5) down to its low flows (Q95) — a steep curve means a flashy river.
The physical character of the land that drains to this gauge, and how it shapes its flood response — from the National River Flow Archive (UKCEH).
Baseflow Index
0.42
mixed response
Avg Annual Rainfall
653 mm/yr
1991–2020 · +2% since 1941–70
Urban Extent
49%
heavily urbanised
Highest Daily Mean Flow
11.80 m³/s
13 Oct 1993 · daily mean, not the instantaneous peak
Flow-Duration Curve
Daily flow (m³/s) exceeded each % of the time — a steep curve is flashy, a flat one is steady. Q5 high · Q50 median · Q95 low.
Land Cover (2023)
Woodland 2%Grassland 27%Arable 2%Urban 68%
Flow affected by: groundwater abstraction.
Photos
Gauging-station photographs from the National River Flow Archive (UKCEH).
The station is located in the lower catchment of the River Crane, just above the confluence with the River Thames in London. The Crane splits upstream of the gauging station at Mereway Flood Defence Gate. A feed is taken into the Duke of Northumberlands river and flows through Mogden sewage treatment works, whilst the main channel of the Crane continues down through Marsh Farm gauging station.
More detail
The catchment
Very flat catchment. The drainage network is difficult to delineate. Mainly urban; catchment contains Heathrow Airport and several pumped storage reservoirs (abstracting from Thames).
The station
Rectangular critical depth flume (insensitive) in a straight concrete channel. Capacity approx. 30 cumecs; yet to be exceeded.
How it measures flow
Theoretical rating; modular limit to be determined. Fish and eel passage were installed at Marsh Farm on 8/9th June 2021.
Flow regime
Substantial artificial influence on flow pattern, evident at low flows: sewage effluent, automatic weir upstream at Mereway Flood Defence Gate that diverts flow into the Dukes River (may result in negligible flows), and considerable area of gravel workings. Mereway Flood Defence Gate was refurbished between February and March 2020. Problems with the refurbishment have meant the gate was subsequently manually altered to maintain a suitable operational level, causing irregular flow patterns at Marsh Farm. Some natural runoff gain from the River Colne catchment (but unlikely to compensate for the upstream diversion).
Timing, not cause. Gauges can move together simply because the same rain fell on both.
Frequently asked questions
Is the River Crane at Marsh Farm flooding today?
The current level is 0.03m, which is within the typical range of 0.02 to 1.55m. Flooding is unlikely at this level.
Is the river level rising or falling at Marsh Farm?
Based on the most recent readings, the level is currently steady. The chart above shows the last 12 hours of measurements by default (up to 7 days), updated roughly every 15 minutes.
Why is the level slowly falling?
When little or no rain has fallen for a while, a river level gradually drops as the water stored in the ground and soil drains away with nothing to replace it. This is called baseflow recession and is normal in dry spells. A gentle decline like this is expected and is not a sign of a problem — downstream gauges often recede a little faster than headwaters further upstream, and levels recover once rain returns.
What is a normal level for the River Crane at Marsh Farm?
The typical range at this station is 0.02m to 1.55m, based on Environment Agency historical data. Levels above 1.55m are higher than usually seen and may indicate a flood risk.
How often is this river level data updated?
Readings are supplied by the Environment Agency gauge. FloodRadar checks for updates roughly every 15 minutes; the timestamp above shows how recent the latest available reading is.
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📮 Flood risk by postcode near this gauge
Postcodes within 5 km with properties in the Environment Agency’s rivers-and-sea flood-risk bands:
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