GUIDE TO THE RIVER THAMES
Mapledurham Weir, River Thames
Mapledurham is located 40 miles west of Central London, in the heart of the Thames Valley, on the western edge of Reading. Mapledurham village, and the stately home of the same name, are situated on the northern side of the river, however the river bank is private and access to the weir is from the southern side of the river via Purley village (SU 6684 7681).
'Small but perfectly formed'. A wide shallow, open chute in the middle of the weir complex that generates a small, friendly 6.1m/ 20 ft wide and 0.6m/ 2ft high wave, part green, part stopper.
When the Thames is in spate and the usual venues are washed out- even Shepperton- Mapledurham is the final refuge for the play boating addict. This is a rare event- some Winters the Mapledurham wave never works- but when it happens, the locals in the know that make it to the weir enjoy a sweet wave that is small but perfectly formed.
Water levels required
If flooding is making it onto the 6 O'Clock News and ruining lives, it's time to check out Mapledurham. For there to be any chance of Mapledurham working, Hurley will be on a big scary 4 gates and 'in the stanchions' and Shepperton will be washed out- although even these conditions are no guarantee. The chances are that the river will be breaching its banks in places. It takes a lot of water to keep the Thames at this level and the river can drop off within 24 hours- as fast as the Environment Agency can manage because these are flood levels.
Gauge and levels information
There is a (tail) gauge at the downstream end of the lock that is readily visible from the southern bank. The wave is usually at its retentive best when the weir pool level is between 11ft 9" and 13ft 0". The optimum level is probably about 12ft 6". Between 11ft and 11ft 9" the wave gradually starts to get more retentive; above 13ft the wave becomes more and more flushy as it starts to wash out.
The weir pool level varies greatly and can rise and fall quickly. Driving all the way to some hard to find location on the western edge of Reading on the off chance that the weir pool might be at the right level isn't worth the hassle- all the more reason to be grateful for the Internet. When the river's high, the chances are that a day won't go by without a local boater checking the weir out, and the more public spirited ones posting news on www.thamesweirproject.co.uk.
Directions and parking
From Reading town centre- head west from the Inner Distribution Road (IDR) following signs for the A329 and Pangbourne. Keep going for 3 miles, and shortly after the 4th roundabout, where the A329 heads right, take a right turn signposted 'Purley Village'. The road takes you down to and over a small humped back railway bridge. Immediately afterwards the road turns to the right- turn left and park up. Straight ahead at the junction, heading north east, is a footpath along the edge of the village behind gardens. Carry your boat down this track and across a field and after 700 yds you will arrive at the river, just down stream of the lock, and opposite the gauge. An alternative is to access the river at Riverside Drive. To get there, follow the road to the right instead of parking up, take the 1st left and then turn right at the end of the road. After 300 yds, park up in the car park on the left in front of the local community centre. Carry your boat further down the road (marked Private Road) and put on to the river straight ahead. Head upstream - the weir is 500 yds away.
Sitting in the weir pool below the weir, and looking upstream, from left to right, you will see the lock, followed by concrete shelving, radial gates, the play boating wave and then more shelving, combined with small sluice gates. Stick to the wave- other parts of the weir complex are dangerous. The wave can be accessed from both sides but less energy is required via the right hand eddy. The eddy is user friendly- sizeable and calm.
The wave is generated by a 6m/ 20ft wide open sluice with a shallow concrete ramp under the water. The weir is set at an angle to the river and as a result flow from above bends to the right as it enters the weir, creating an asymmetric wave. Looking upstream, when the gauge reaches 12ft, the right hand side of the wave consists of a gentle stopper and the left hand side, a green wave. The upstream ramp of green water is almost horizontal. The result is a very user friendly venue- excellent for play boating beginners but good for new school moves- wheels and blunts- although this is not a big powerful wave and good technique and a 2m boat are required to get genuine 'air time'.
CONTRIBUTED BY: Chris Wheeler.