Upper Lee catchment
• Birch Green • Hertfordshire • ID: 4690TH • Level
(36m ago) • 4 readings/hr • 148 views
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⤴Unusual rise — FloodRadar+Top 1% rise rate for this gauge.
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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.
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EA/SEPA/NRW data and are best-efforts. Terms
Current Level
0.106 mASD
▬ Steady
24h Max
0.133 mASD
24h Min
0.104 mASD
Typical Range
0.12 - 0.60
mASD
Highest Recorded
1.16 mASD
EA official record
1.12 in our data (since Oct 1985)
Current level is 9% 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 8 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.
24 storm overflows are traced upstream of this gauge, the nearest 3.4 km away along the river. 0 report discharging now, 19 report not discharging, and for 5 the monitor is offline or has not reported, so their status is not known.
Thames Water · into Wood Hill Brook · 3.4 km away in a straight line · no mapped watercourse close enough to be sure
0 spills · 0 hours in 2025
Not discharging now · last
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 Birch Green flood history.
Flood areas linked to this gauge
Flood warnings and alerts are issued for whole areas. These are the 11 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
0.69
groundwater-fed — slow & steady
Avg Annual Rainfall
673 mm/yr
1991–2020 · +3% since 1941–70
Urban Extent
20%
heavily urbanised
Median Annual Flood
7.20 m³/s
QMED — typical yearly peak flow
Highest Daily Mean Flow
9.98 m³/s
16 Sep 1968 · 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.
Station located in the Upper Lee catchment above the confluences of tributary rivers.
More detail
The catchment
Catchment is mainly pervious (Chalk) but with glacial Drift in the headwaters. The land uses are principally agricultural with some important (expanding) urban centres.
The station
Crump weir approximately 6m wide. Present station built in October 1971 to replace two temporary stations at Waterhall Farm and Roxford Farm. River course altered for gravel works and current station was built within this new artificial section.
How it measures flow
Modular throughout the flow range. Standard Crump weir calculation. Theoretical rating has a reasonable level of accuracy. Approach channel can become heavily choked with vegetation and has to be regularly managed.
Flow regime
There is storage capacity in Luton Hoo lakes and the station is downstream of the outfall from an ornamental lake. Flows are substantially reduced as a result of groundwater abstraction (significant export). Considerable interludes of zero flow, occasionally interrupted by small sluice releases (above the thin-plate weir). Some surface water drainage from Luton bypasses the gauge via the East Hyde sewage treatment works. Rununculus growth in upstream section is rampant in the growing season. Cutting does occur on a regular basis but can lead to minor drift adjustment of water level.
The flow record
All flows contained. Some early data (of limited quality) from two nearby gauging stations. There was a station on the River Lee at Roxford (38801) which, started in November 1952. In order to produce a single record, some correlations were undertaken between these stations. They had an overlapping record from September 1971 to August 1972. These were compared and a formula was used to derive Water Hall values. Full period of record peak flow data reviewed and released in September 2019 (WINFAP Files v8).
How this gauging station is built and how long it has measured (NRFA / UKCEH).
Gauge type
Crump weir
Operating since
1971
Station datum
43.6 mAOD
Flow record
1959–2024 · 65 yrs · 100% complete
Peak-flow record
since 1952
Hydrometric area
38
Measured by
Environment Agency
Nearby Groundwater
Soil Moisture
Possible storm-overflow correlation
Frequently asked questions
Is the River Lee at Waterhall flooding today?
The current level is 0.11m, which is below the typical range. Flooding is very unlikely at this level.
Is the river level rising or falling at Waterhall?
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.
What is a normal level for the River Lee at Waterhall?
The typical range at this station is 0.12m to 0.60m, based on Environment Agency historical data. Levels above 0.60m 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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