GUIDE TO THE RIVER THAMES

(Hambleden Weir)

Name
Hambleden Weir, River Thames.

Location
Located 30 miles west of Central London, in the heart of the Thames Valley, between Henley and Marlow. The weir is situated at Mill End- south of Hambleden Village itself- and is the next weir upstream of Hurley. Both these villages are north of the river although the usual access point for visiting paddlers is on the southern side of the river (SU 7826 8513).

Characteristics
The main weir consists of 4 large radial gates that can, when the weir pool level is low and/or the underwater ramps are raised, generate a large green, partly breaking, wave with big boily eddy lines- a useful, less crowded, alternative to Hurley.

Introduction
Hambleden was a major white water venue long before the emergence of Hurley and Holme Pierrepont. White water canoeing has taken place at the weir pool since the 1940s and it was the training ground for the British Slalom team during the 1950s and 1960s and for the 1972 Olympic team. Over 100 slalom events were held at the weir between 1951 and 1996. It has also been a popular play boating venue, long before the term was invented, in the days when people played in longer boats.

All this changed however, in 1996, when the Environment Agency rebuilt the main weir. The new weir was far too efficient for its own good, resulting in a flushy wave instead of the old classic surf wave and wave train.

Following pressure from the local club, Chalfont Park, and the BCU, the EA commissioned George Parr of Nottingham University's Hydraulic Engineering Department (designer of the Holme Pierrepont white water course) to carry out a study to see if the wave could be restored.

Over the Summer of 2002 work was carried out to create underwater ramps that can be raised and lowered using air filled cushions that are pumped up using a cylinder of compressed air. These enable members of Chalfont Park to raise the ramps to suit the water level at the time to create a retentive wave with wave train. The ramps have a base level of 15 degrees, increasing to 30 degrees when raised.

As English White Water went to press, attempts were being made to solve one problem that had become evident, namely that the ramps could only be kept open for short periods due to the need to maintain a flow of compressed air into the air cushions. A solution was being sought whereby a non return valve was to be fitted, assuming that the air cushions would not leak air. As a result, the ramps have been down at their base level most of the time.
Local paddlers have been busy trying out the weir at different levels, with or without the ramps raised. The good news is that, when the weir pool is low enough, even without the ramps raised, a green, partly breaking, retentive wave does form.

UPDATE, OCTOBER 2003 - the Hambleden work has hit a bit of an impasse, with alleged disagreements between various parties involved. The Thames Weir Project website carries more info here and here.

Water levels required
Normal Winter levels, typically when Hurley is on 2 to 4 gates. However, when Hurley is on a high 4 gates and Shepperton has started to work, the chances are that Hambleden will be washed out.

Gauge and levels information
The Hambleden wave is not predictable like Hurley and it is recommended that paddlers check the latest news on www.thamesweirproject.co.uk before travelling.

Directions and parking
The weir is can be inspected from the northern side of the river, where Chalfont Park Canoe Club are based. However, car parking is limited and if you are not a club member then the nearest car park is 500 yds away on the road to Hambleden Village.

Visiting paddlers usually access the weir from the southern side of the river. Directions are similar to those for Hurley- Hambleden is the next weir upstream of Hurley, 2 miles further west, heading towards Henley.

From the M4-exit at junction 8/9 and head north on the A404(M), following the signs for High Wycombe. Turn off after 4 miles, onto the A423, following the signs for Henley and Hurley. After 3 miles, after the Hurley turn off, at a dip in the road at Remenham Hill, turn right following the signs for Aston. Fork right at the Flower Pot pub and carry on until the road ends, at the river, where there is a small car park.

From the M40- exit at junction 4 and head south on the A404, following the signs for Maidenhead. Turn off after 5 miles, following the signs for Henley, heading west on the A423 for 3 miles, past the turn off for Hurley- directions are then as described above.

From the car park, paddle upstream 500 yds and you will reach the weir.

Description
Looking upstream from the weir pool, from left to right, there is the lock, followed by a small island; 2 small radials; a long tiered concrete shelf, the 4 radial gates of the main weir; another long tiered concrete shelf; 2 further radial gates; further shelving and a further, triple, radial. The weir structure zig zags from one end to the other, at an angle to the river, and as a result the main weir and radials nearest the lock are both tucked into corners with limited access from one side. The water drops a greater height at Hambleden than at Hurley.

The main weir consist of 4 large radial gates, which looking upstream from the weir pool, can be numbered 1-4 looking from left to right, from the main eddy. With the weir pool level is low enough and/or the underwater ramps are raised and at least 1 gate is open, the weir generates a wave train which is good for slalom training. Play boaters will however, want to see at least 2 gates open because this is needed to produce the new Hambleden wave. The top wave can be up to 30ft wide and 4ft high, depending on the weir pool level and whether the ramps are raised. When the weir pool is relatively low and/ or the ramps are raised, the wave can be largely green, at other times the wave can be breaking and very retentive. The wave is suitable for the basic moves- front and back surfing and flat spins and ends and new school moves such as blunts are achievable.

Whilst the wave may not be as good as Shepperton at its best, it is a useful, less crowded and more user friendly alternative to Hurley.

The other smaller radials are dangerous most of the time- producing retentive stoppers between the stanchions. However, they do provide useful moving water downstream for training and experienced paddlers may find that at certain levels it is possible to play in the stoppers- but be very careful.

Comments
Beware- at certain levels, typically when the weir pool level is relatively high, the top wave can turn into a very retentive stopper. Check carefully- it should obvious from the eddy what you are about to let yourself in for.

So, will Hambleden solve the overcrowding problem experienced at Hurley due to the growing popularity of play boating or will it get as busy as Hurley, as demand catches up with supply? Only time will tell.

The pub that you pass in your car as you near the river - The Flower Pots - is recommended - it has a very nice garden.

CONTRIBUTED BY: Chris Wheeler.

 

 

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