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0.35

North Mymms

Mimmshall Brook
Colne (Upper) catchment • Water End • Hertfordshire • ID: 2810TH • Level
(21m ago) • 4 readings/hr • 136 views

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⤴ Unusual rise — FloodRadar+Top 1% rise rate for this gauge.
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Current Level
0.354 mASD
▬ Steady
24h Max
0.357 mASD
24h Min
0.354 mASD
Typical Range
0.05 - 1.50
mASD
Highest Recorded
2.35 mASD
EA official record
A 3.46 reading (30 Oct 2000) sits in our unverified raw history and is not treated as the record
Current level is 15% of this
🚽 Sewage overflows nearby

Recent Water Levels

🌍 floodradar.co.uk
1 day

Recent Readings

Steady over 5h
10 Oct 13:15 ▬ steady 0.354 mASD
10 Oct 13:00 ▬ steady 0.354 mASD
10 Oct 12:45 ▼ -0.1 cm 0.354 mASD
10 Oct 12:30 ▲ +0.1 cm 0.355 mASD
10 Oct 12:15 ▬ steady 0.354 mASD
10 Oct 12:00 ▬ steady 0.354 mASD
10 Oct 11:45 ▼ -0.1 cm 0.354 mASD
10 Oct 11:30 ▬ steady 0.355 mASD
10 Oct 11:15 ▬ steady 0.355 mASD
10 Oct 11:00 ▬ steady 0.355 mASD
10 Oct 10:45 ▬ steady 0.355 mASD
10 Oct 10:30 ▬ steady 0.355 mASD
10 Oct 10:15 ▬ steady 0.355 mASD
10 Oct 10:00 ▬ steady 0.355 mASD
10 Oct 09:45 ▬ steady 0.355 mASD
10 Oct 09:30 ▬ steady 0.355 mASD
10 Oct 09:15 ▬ steady 0.355 mASD
10 Oct 09:00 ▬ steady 0.355 mASD
10 Oct 08:45 ▬ steady 0.355 mASD
10 Oct 08:30 0.355 mASD

Station Details

  • Monitoring Station: North Mymms
  • Watercourse: Mimmshall Brook
  • Nearest Town: Water End
  • County: Hertfordshire
  • Coordinates: 51°43'5"N 0°13'9"W (51.718066, -0.219123)
  • Open in: Google Maps · Apple Maps (opens your maps app)
  • Date Opened: 1 Jan 1985
  • Status: Active
  • Station Type: River level station
Technical details: references, datum, range, flow archive
  • Station Reference: 2810TH
  • RLOI id: 7177 (the EA's check-for-flooding station id)
  • EA Gauge ID: 2810TH-level-stage-i-15_min-mASD
  • Parameter: Level
  • Unit: mASD
  • Typical rise rate: 14 cm/hr (p95 sustained over 90 days)
  • Typical data delay: ~22 min (measured reading→publication lag)
  • Tidal: No
  • Lock / structure: No
  • Catchment Area: Colne (Upper)
  • Typical Range: 0.046 – 1.500 mASD
  • EA Cross-check: 0.35 mASD (EA at 10 Oct 12:45)

Geographic coordinates may reflect the access point for the gauge, and not the precise location in the watercourse that it is taking readings from.

Nearby Stations

Gauges connected to this river, and others nearby. A distance “by river” follows the river on the map; any other is in a straight line.

Connected upstream

Connected downstream

Same river system, separate branch

Distances by river: OS Open Rivers. Contains OS data © Crown copyright and database rights 2026.

💧 Storm overflows upstream of this gauge

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.

1 storm overflow is traced upstream of this gauge, the nearest 3.7 km away along the river. 0 report discharging now, 1 reports not discharging.

💧
Thames Water · into Potters Bar Brook · 3.7 km upstream along the river
9 spills · 25 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 →

Contains OS data © Crown copyright and database rights 2026.

Rainfall & Weather

Loading rainfall and weather data...

How often this river runs high

This gauge rarely reaches its typical high of 1.50 m: 4 days since 2017. This year so far: 0 days.

2026 0 days so far
2025 0 days
2024 1 day
2023 1 day
2022 0 days
2021 2 days
2020 0 days
2019 0 days
2018 0 days
2017 0 days

Counted from each day's highest reading. Days with missing or implausible readings are left out.

Flood history near this gauge

Official Environment Agency warnings issued since 2009 for the 6 flood areas linked to this gauge (nearest 0.4 km away).

5flood warnings 10flood alerts

Most recent flood warning: 19 Jul 2025 — Radlett and Borehamwood Brooks at Borehamwood

Year by year
YearWarningsAlerts
2025 1 0
2024 0 2
2021 1 1
2014 2 3
2012 1 2
2010 0 1
2009 0 1

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 Water End flood history.

Flood areas linked to this gauge

Flood warnings and alerts are issued for whole areas. These are the 6 areas linked to this gauge, nearest first.

Frequently asked questions

Is the Mimmshall Brook at North Mymms flooding today?

The current level is 0.35m, which is within the typical range of 0.05 to 1.50m. Flooding is unlikely at this level.

Is the river level rising or falling at North Mymms?

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 Mimmshall Brook at North Mymms?

The typical range at this station is 0.05m to 1.50m, based on Environment Agency historical data. Levels above 1.50m 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:

Check any UK postcode’s flood risk →

🏠 Buying or renting around here? Get the Property Flood-Risk Report for any English postcode — official risk band, recorded floods, warning history, river behaviour and nearby storm overflows. £19 one-off. Learn more →