Flooding on the Dorset Stour at Bear Mead.

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*** Stour FLOOD: Estimated peak times at following places: Gillingham | Hammoon | Blandford | Wimborne | Ensbury | Throop | See Twitter @Bearmead for these times and dates.

This private website gives measured river and groundwater levels, together with expected arrival time at Bear Mead of any sizeable rain-surge coming downstream. Compiled by the landowner at Bear Mead .

Bear Mead is located 1.5 miles upstream of Wimborne Minster on the South Bank of the Dorset Stour, immediately West of Eye Mead (National Trust) and North of the A31. It is a private Nature Reserve of 25 acres, 5 fields of flat flood plain. It floods when the river height is greater than 350.

River and groundwater levels

05 Mar 2012 - 02 Apr 2012 03 Apr 2012 - 1 May 2012 123456789012345678901234567890123 FLOOD-12 -13 02 May 2012 - 30 May 2012 -14

Prediction of rain-surge arrival at Bear Mead.

Graphs and forecast by the landowner based on Environment Agency data of latest river levels at Gillingham, Hamoon, Blandford, Wimborne, Ensbury and Throop. High water 14 at BEAR MEAD expected 1200 hrs 11may2012 (240) (Tentative only) Calculations for next High Water 14 Peak at Gillingham....1900 10may2012 +17 hrs delay Peak at Bear Mead....1200 11may2012 Sector distance GH HB BT Total 21 + 11 + 25 = 56 miles Wave Sector delay 01 22 + 11 + 17 = 50 hrs 02 16 6 13 35 05 22 6 14 42 11** 6 9 39 54 12** 15 8 38 61 13** 19 9 31 59 14 6 5 13 25 Hrs Sector Distinguishing features 22 01GH 1st high water of season (clearing vegetation) 22 05GH Still clearing small tributaries 6 11GH After 6 weeks drought (compacted earth) 6 14GH Upper Stour still saturated 11 01HB 1st high water of season (clearing vegetation) 17 01BT Flood plains NOT entered 13 02BT Flood plains NOT entered 39 11BT Flood plains entered 38 12BT Flood plains entered 31 13BT Flood plains entered

In the wet season (Nov-Apr), each rain surge downstream tends to smooth the way for the next surge, shortening the overall river travel time from Gillingham to Throop, and hastening its arrival at Bear Mead. Uneven rain distribution across the catchment area and inputs from tributeries complicate any predictions. During a FLOOD, the surge has to fill ever-increasing flood plains before advancing, slowing the progress of the peak. -Author "Travel time in rivers is a combination of factors particularly the roughness (Mannings n) which is a factor of vegetation growth etc... The first event December 13th was the first big 'flush' of the season. This is likely to have flushed away a lot of dead or dying vegetation reducing frictional losses (Mannings n) shortening the travel time."-Env.Agency

Floods since July 03: Analysis of Floods 2003 none | 2004 none | 2005 Dec 3 | 2006 Nov 26, Dec 31 | 2007 Mar 6 | 2008 Jan 16, Mar 17, Dec 15 | 2009 Feb 10, Nov 30, Dec 4, Dec 9 | 2010 none | 2011 none | 2012 Apr 27, May 01, May 04 |

Past Records: Graphs (101 months) Numbers (101 months) Location Display by year Averages Statistics Travel Times

River height Highest recorded=385 Height at flood=355 Average over year=160 Lowest recorded=110

Floodplain state 0% flooded

River temp: 4°C River pH:    8.21 Last Flood: 9 Dec 2009

My Guestbook Other Stour Levels

Length of Dorset Stour The river is over 72 miles from Source to Mouth. The length of the Stour, along the river including all meanders, was measured by using Google Earth with 'Tools-ruler-path' facility, together with Philip's Street Atlas 3.5in=1mile. The Stour rises at St Peters Pump, near Stourhead, but can be under the surface for some distance in dry months. It reaches the sea in Christchurch Harbour.

About the Dorset Stour Length: 100km, Catchment area: 1,300km2, Population: 400,000, Rainfall: 697-1131 mms/year, Flood season: Nov-Mar, Land use: 8% urban, 52% arable, 34% grassland, 6% other. Because much of the river's course is across clay soil, the river's waterlevel varies greatly. In summer, low water level makes the river a diverse and important habitat, supporting many rare plants. In winter, the river often floods, and is therefore bordered by wide and fertile flood plains. Eye Mead floodplain is pasture 1,000 metres wide, and 19 metres above sea level.

When the River floods Pictures of degrees of flooding at Eye Mead. 0% | 2% | 5% | 10% | 20% | 30% 40% | 50% | 60% | 70% | 80% | 95% Bear Mead, 1km upstream (right), not visible to photograph. Floodplain stretches 1km beyond (South) of River

The Dorset Stour floodplain, pictures centred on Eye Mead, SY 995-995, Eye Bridge left foreground, (see flooding progress). FL3118. 27 Apr 2012. 1000 hrs. River height=360. Fields 50% flooded. (Unusual flood,in Spring, after 7 weeks of drought)

Future rain: Rainfall predicted over the next 24 hours by the BBC Weather Centre. The river responds in 24 hours to heavy rain. The river falls equally quickly. Also see: 5-day forcast Location of Bear Mead: Bear Mead is about 5 miles North West of Poole Harbour, Dorset, England

BBC Weather Forcast for this area Work out the probable amount of rain that will fall, and how it will affect the height of the river. 5 Day-FORCAST Hourly-RAIN Hourly-CLOUD Hourly-TEMPERATURE Hourly-WIND Jetstream

Rule of Thumb: The difference when stable between height of the Watertable (W) and River (R) decides the response of the River to Rainfall. If (W+60-R) is negative (dry ground), the River will hardly rise even after 30 mms of widespread Rain. If well positive (wet ground), the River may rise 250 cms in 24 hours for 30 mms of Rain. (W+60-R) usually becomes negative about early June and positive again about mid October, conveniently defining the dry season (summer) and wet season (winter). (W+60-R) has been observed with steady values in the range of +100 to -13. Present value of: (W+60-R)= +6 (wet)

A record of the Rainfall, Watertable and River Level of the River Stour at Bear Mead, about 2 miles West of Wimborne Minster, Dorset. Contact the author at for more information. see also: TIDAL TRENCH to control flooding. Unblocking, Tidying, Theory & early results, Results during flooding Mill Stream ditch

This website tries to give simple answers to questions about flooding on the Dorset Stour at Bear Mead. Where is Bear Mead? See Location What do the fields look like when flooded? See the pictures below How high does the watertable have to be before the fields flood? 220 cms How much rainfall is needed to make the river flood? About 10 mms rain for every 10 cms below watertable of 220 When is it likely to flood? When the watertable is about 200 cms (but depends how much rain arrives in next 36 hours)

How quickly will it flood? About 33 hours after heavy rain starts. How quickly will the flood disappear? About 48 hours after heavy rain stops. How deep underground is the watertable? (220-L) cms where L is the watertable level given above Are there past records for water levels? Yes, see Numbers. Are there graphs of how past levels have changed? Yes, see graphs. How has the river flow varied since 1968? See Flow

State of Flooding on the River Stour

Bear Mead sometimes floods after prolongued rain in the winter. The flood plain is 1200 yards wide at this point. There are spot OS heights of 19 meters, in Field 3 and on the access bridleway "D". The nearest official calibrated river height scale is at Corfe Mullen Mill, 1.5 miles up stream, easily read from the A31. There is a well in Field 5, enabling the water table to be monitored. An unofficial scale has been placed in the river at Field 1. Rainfall is monitored daily at the Author's home, 2 miles away. The official calibrated river height scale at Julian's Bridge, Wimborne showed 16.9 metres when the river at Bear Mead indicated 150 cms, so Bear mead should flood when the official scale reads 18.6 metres (assuming the weir near Eye Bridge has no effect). Similarly, the scale at White Mill showed 21.4 metres, and should read 23.10 when Bear Mead floods. These pictures, taken in 2000, show what happens when the floodplain floods. They were taken from Eye Bridge, because it is not possible to get onto Bear Mead itself without a landing craft! The floods usually arrive quickly but also depart quickly, leaving the ground very soggy indeed. The depth of the water-table is a good measure of the "sogginess".

6. The Stour and floodplain.

8. Approach bridleway to Bear Mead, 15 Nov 2002.

7. Car park at Eye Bridge

Bear Mead 14 Apr 2004

River Stour at normal height in Spring (145 cms)

26 Jun 2009. Thunderstorm over Poole, Dorset. 30mm rain in 9 hours

26 Jun 2009. Local rain runs into ditch then into river. Hump=250.

Flood delay in hours "It takes time for rain which falls over the catchment area to be converted into river flow and any floodwater which builds up takes time to flow downstream to the sea". SWGFL. Bear Mead is 33 hours downstream of rain Map of Catchment Area | Recording Stations Historic Flood Rainfall Figures: Source: swgfl Year Month Total Interval Max/Day (mm) (Days) (mm) 1894 Dec 141.1 7 36.0 1916 Nov 134.7 8 29.0 1916 Dec 104.0 6 44.0 1933 Feb 89.9 3 56.0 1943 Feb 94.2 8 26.0 1954 Dec 84.9 5 27.0 1966 Nov 68.8 4 56.9 1979 May 105.6 11 35.0 1979 Dec 86.1 5 57.8 1990 Feb 78.0 6 25.0 1999 Dec 90.9 6 30.5 2000 Oct 80.2 6 35.0 Floods recorded on this website: 2005 Dec 30 2 22 2006 Nov 54 4 21 2006 Dec 54 3 27 2007 Mar 53 4 19 2008 Jan 42 3 26 2008 Mar 26 3 16 2008 Dec 20 1 20 2009 Feb 40 2 28 2009 Nov 37 2 23 2009 Dec 38 2 22

Nov-Dec 2009. The number of visitors to this website follows quite closely the height of the river, or perhaps my warning of a flood! If you are one of these users, please email and tell me your interest.

Links to Environment Agency Hammoon......@ 18hrs upstream Blandford......@ 12hrs upstream Bear Mead....@ this website Oakley..........@ 1hr downstream Woodyates groundwater @ site datum 102m Monthly Water situation report contains: Summary, Rainfall, Soil Moisture Deficit, River Flows, Groundwater Levels and Reservoir Storage for past month

Length of Dorset Stour The river is over 72 miles from Source to Mouth. The length of the Stour, along the river including all meanders, was measured by using Google Earth with 'Tools-ruler-path' facility, together with Philip's Street Atlas 3.5in=1mile. The Stour rises at St Peters Pump, near Stourhead, but can be under the surface for some distance in dry months. It reaches the sea in Christchurch Harbour.

Compiled, formatted, hyperlinked, encoded, and copyright © 2004, John Palmer, All Rights Reserved.