Upper Lee catchment
• Birch Green • Hertfordshire • ID: 4690TH • Level
(47m ago) • 4 readings/hr • 117 views
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⤴Unusual rise — FloodRadar+Top 1% rise rate for this gauge.
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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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Current Level
0.122 mASD
▬ Steady
24h Max
0.131 mASD
24h Min
0.106 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 11% of this
🚽Sewage overflows nearby
Recent Water Levels
🌍 floodradar.co.uk
1 day
Prediction V2
Prediction Eris
Nimbus beta
Experimental model fusing soil moisture, river flow, groundwater and catchment
character. Shown with its calibrated 10–90% confidence band. 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.
Long Term
🌍 floodradar.co.uk
—
Consecutive rainy days0 → 10+
Days Above Normal
This year vs 5-year monthly range
Recent Readings
Falling · -0.8 cm over 6h
23 Aug 23:45▼ -0.1 cm0.122 mASD
23 Aug 23:30▼ -0.1 cm0.123 mASD
23 Aug 23:15▬ steady0.124 mASD
23 Aug 23:00▼ -0.2 cm0.124 mASD
23 Aug 22:45▼ -0.1 cm0.126 mASD
23 Aug 22:30▼ -0.4 cm0.127 mASD
23 Aug 21:15▬ steady0.131 mASD
23 Aug 21:00▬ steady0.131 mASD
23 Aug 20:45▬ steady0.131 mASD
23 Aug 20:30▬ steady0.131 mASD
23 Aug 20:15▬ steady0.131 mASD
23 Aug 20:00▬ steady0.131 mASD
23 Aug 19:45▬ steady0.131 mASD
23 Aug 19:30▬ steady0.131 mASD
23 Aug 19:15▬ steady0.131 mASD
23 Aug 19:00▬ steady0.131 mASD
23 Aug 18:45▬ steady0.131 mASD
23 Aug 18:30▬ steady0.131 mASD
23 Aug 18:15▲ +0.1 cm0.131 mASD
23 Aug 18:000.130 mASD
Rainfall & Weather
Loading rainfall and weather data...
Flood history near this gauge
Official Environment Agency warnings issued since 2008 for the 12 flood
areas linked to this gauge (nearest 2.2 km away).
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.
Geographic coordinates may reflect the access point for the gauge, and not the precise location in the watercourse that it is taking readings from.
Catchment Character
🌊 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 Recorded Flow
9.98 m³/s
16 Sep 1968
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
🚽 Storm overflows on this river
Frequently asked questions
Is the River Lee at Waterhall flooding today?
The current level is 0.12m, which is within the typical range of 0.12 to 0.60m. Flooding is 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 7 days of measurements, 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 taken by the Environment Agency gauge roughly every 15 minutes and FloodRadar refreshes its data continuously, so the level shown is normally less than an hour old.
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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:
