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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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Not an emergency service — if in danger call 999. Alerts rely on
EA/SEPA/NRW data and are best-efforts. Terms
High tides on Sunday may lead to flooding.
Flooding is possible for 1 hour either side of Sunday evening's tide at 22:30 on 25/10/2026.
The weather increases tide table values by 0.48 m. Total forecast tide is 5.24 metres Chart Datum (2.50 mAOD) at Chichester Harbour. The tide will flood Shore Road. At Bosham High Street, water will be near to or flood front door steps. Land of shore side properties around the Harbour could also be affected. Monday morning’s tide at 11:00 on 26/10/2026 is forecast to be 15cm higher.
A Flood Warning will be issued for Monday morning’s tide and isolated property flooding is expected in Bosham.
Monday evening’s tide at 23:00 will be lower and no further flooding is predicted.
We are closely monitoring the situation .
Consider activating any flood protection products you may have.
This message will be updated by 6:00PM on Monday 26 October or as the situation changes.
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 23 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.
1 storm overflow is traced upstream of this gauge, the nearest 810 m away along the river. 0 report discharging now, 1 reports not discharging.
Southern Water · into Ports Creek · 4.6 km away in a straight line · discharges to the sea, an estuary or tidal water
11 spills · 28 hours in 2025
Not discharging now · last
5 more within 6 km whose connection is not known.
1 other overflow within 6 km is downstream of this gauge or on another branch of the river network, so it is 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. Sewage & storm overflows →
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 Havant flood history.
Flood areas linked to this gauge
Flood warnings and alerts are issued for whole areas. These are the 35 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
0.25
flashy — rain runs off fast
Avg Annual Rainfall
877 mm/yr
1991–2020 · +5% since 1941–70
Urban Extent
24%
heavily urbanised
Median Annual Flood
9.42 m³/s
QMED — typical yearly peak flow
Highest Daily Mean Flow
5.52 m³/s
27 Dec 1979 · 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 22%Grassland 29%Arable 1%Urban 48%
Grassland 26% → 29% since 1990
Photos
Gauging-station photographs from the National River Flow Archive (UKCEH).
Velocity area station in a concrete trapezoidal section within a formalised reach. Station gauges a mainly impervious catchment, typical hydrograph very flashy. Post-2003 complex water utilisation affects flows.
More detail
The catchment
A mainly impervious catchment, principally Reading Beds and London Clay. Intensive suburban development since the early 1960s, lower catchment now heavily urbanised.
The station
Velocity area station, 5.36m wide in a concrete trapezoidal section. Formalised reach with grass berms beneath a bridge; concrete block wall higher on outside of bend on right bank.
How it measures flow
Structure designed to measure up to 14 cumecs; all but exceptional flows contained and structure only exceeded a few times since installation. Bridge downstream may cause some backing up. Trolleys often thrown into stream here. Very sensitive at low flows, to extent where anomalous flow patterns occur (e.g. 2008); despite low flow anomalies, weed growth is not an issue at this station (very poor site ecologically). In 1951 a step was inserted into the flume throat to ensure modularity over the whole flow range, as the channel downstream was unlined. This was removed in 1956 and the structure became non-modular for low flows. One rating applied across period of record. Rating theoretically based but numerous current meter gaugings for this site.
Flow regime
Typical hydrograph very flashy; responsive regime. Natural to within 10% at Q95. Post-2003, some augmentation of high flows by runoff from the adjacent catchment of the Lavant Stream. Flow is diverted via a pipe into the Hermitage Stream, whenever the flow in the Lavant exceeds 0.28 cumecs. These inter-basin transfers also affect medium/low flows (e.g. 2006). Storage effect introduced to allow separation runoff from nearby Warren housing estate. Developers arranged 6 hour storage of natural stream runoff before its release into the Hermitage Stream (by which time the hydrograph is on the recession limb). Estate surface water drains allow unfettered discharge.
The flow record
Chart stage record extends back to 1953 providing peak flows pre-1979. June-August 2000 flows considered suspect. Station was possibly abandoned for a short duration around 1974. In winter of 1961, there existed a long period of high baseflow where the contribution from the Lavant catchment may have been greater. Full period of record peak flow data reviewed and released in September 2020 (WINFAP Files v9).
Timing, not cause. Gauges can move together simply because the same rain fell on both.
Frequently asked questions
Is the Hermitage Stream at Havant flooding today?
The current level is 5.10mAOD, which is within the typical range of 5.03 to 6.20mAOD. Flooding is unlikely at this level.
Is the river level rising or falling at Havant?
Based on the most recent readings, the level is currently falling slightly. 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 Hermitage Stream at Havant?
The typical range at this station is 5.03mAOD to 6.20mAOD, based on Environment Agency historical data. Levels above 6.20mAOD 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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11 Jun 2012 High flows
11 Jun 2012 View downstream, high flow
11 Jun 2012 High flows
11 Jun 2012 View upstream, high flow
25 Nov 2009 Measuring section looking downstream
25 Nov 2009 Channel upstream of gauging station
25 Nov 2009 Road bridge downstream of gauging station
25 Nov 2009 View of station and immediately upstream
25 Nov 2009 Cross-section used for measurement
25 Nov 2009 View upstream from left bank
25 Nov 2009 Velocity-area trapezoidal section, looking downstream. Bend in river past road bridge not thought to affect hydrometric performance
25 Nov 2009 Velocity-area trapezoidal section, looking downstream.
15 Nov 2008 View upstream
15 Nov 2008 Measuring section
Downstream view to gauging station