river wey dorset

[ianspaintpot]

i was wondering has anyone ever tryed to find if there is a cave system that feeds the river wey in weymouth as it discharges something like 6-10 million gallons a day 14-16 from all manor of of places in a heavy rain storn.
i know when the wishing well was worn away and fell in ages ago i think some people tryed to get permision to have a poke around but was booted of.
i know it is a cave divers job from the wishing well end but there must be other entrances.

 

[mikem]

Passages in chalk have been discussed at various times:
https://ukcaving.com/board/index.php?topic=2144.0

https://ukcaving.com/board/index.php?topic=11498.0

 

[tim.rose2]

There's a band of limestone that runs from the Wishing Well west to Portesham.  The main chalk ridge is a little North of this.  Over the years I've had a look along side pretty much all the footpaths in that area and never found a thing of interest.  Though the bit behind Upwey church does look particularly 'cavey'.  I think there is potential for limestone caves in that area (as have others), but it's hiding well.  Most of the fields are farmed and so any natural features to give clues long gone. 

The patch between Shipton Gorge and Bridport is also interesting as it contains 1 known cave (Walditch).  There's also limestone between Poxwell and Bincombe as well as a lot in Purbeck - but no known caves.  Personally, on Purbeck I think the ridge from Kingston to Kimmeridge is the most likely patch but again despite numerous walks I've not found anything to get inspired by.  Many others have also looked!

 

[Ed W]

I know the place well, having been brought up only about 300m from the Wishing Well and was there yesterday visiting my parents.

I think that there is a high liklihood of cave development between the wishing well and Portesham, indeed there is another small spring/rising right next to the junction between the roads leading to Friar Waddon and Coryates.  The spring is in a very narrow valley and might repay digging if permission could be gained.

As for the Wishing Well itself, the main rising lies just to the right of the well (looking upstream) and is choked with small stones, though there is the impression of void at times.  The rising can be very impressive and regularly chucks out limestone cobbles about 75mm cubed.  Any exploration would be va underwater digging, which for years was imossible as there was a trout farm just downstream - that has now gone.  However as the well lies in the garden of a cafe I am pretty sure that obtaining permission would be nigh on impossible.

I am led to believe that when the pumping station, about 1 mile away towards Portesham, is operating that the flow from the well immediately drops (I think this suggests that any cave system is Phreatic), but I noted yesterday that the Wey was running very discoloured about 100m downstream of the Well at about 2pm after the rain from Storm Barra in the morning.

Like Tim I have walked pretty much the entire area many times over the last 40 years or so, and there is no obvious place to dig.

 

[Ed W]

silly mistake, should have said left not right of the well...

the main rising lies just to the right of the well

 

[mikekushy]

Am I right in believing there's a fault that runs from the quantocks to Weymouth somewhere aswell?

I'm sure OT mentioned it in one of his posts on here.

 

[Andy Farrant]

The fault that runs SE from the Quantocks is the Watchet-Cothelstone-Hatch Fault (WCHF). This comprises a system of northwest-southeast-trending basement and cover faults that are traceable for at least 40km from the Bristol Channel, southeast into the western Wessex Basin around Ilchester.  This is not the same fault as the Abbotsbury?Ridgeway Fault that runs east-west just north of Upwey and forms part of the larger Purbeck-Wight fault zone

https://mapapps2.bgs.ac.uk/geoindex/home.html?_ga=2.112087878.35143776.1646659009-1189612513.1620999628

 

[Ali M]

The fault that runs SE from the Quantocks is the Watchet-Cothelstone-Hatch Fault (WCHF). This comprises a system of northwest-southeast-trending basement and cover faults that are traceable for at least 40km from the Bristol Channel, southeast into the western Wessex Basin around Ilchester.  This is not the same fault as the Abbotsbury?Ridgeway Fault that runs east-west just north of Upwey and forms part of the larger Purbeck-Wight fault zone

https://mapapps2.bgs.ac.uk/geoindex/home.html?_ga=2.112087878.35143776.1646659009-1189612513.1620999628

Andy - an extremely useful link, thank you.

 

[mikekushy]

A little out the way on the Dorset downs, but still in Dorset. Doesn't Rampisham hill look interesting! From the geological map it looks like 2 faults cross on decent limestone. A quick Google on 'Rampisham farm' and to me it looks like there's also an obvious sinking stream in the farms front garden.

224m elevation, so plenty of scope potentially.

 

[Andy Farrant]

Rampisham hill is on the Chalk, so the scope for significant cave development is likely to be rather limited. But interesting from a hydrogeology perspective. Lots of good springs at the base of the chalk at the contact with the Upper Greensand, but I would very much doubt they would be worth digging. Can't see any obvious stream sinks though.
https://largeimages.bgs.ac.uk/iip/mapsportal.html?id=1001816

 

[NigelG]

Upwey Wishing Well is on the base of the Portland Stone, and becomes discoloured in high flows by the underlying clay. The geology of Upwey is much the same as on Portland as the site is on the North limb of an unsymmetrical anticline, deeply eroded to produce the Weymouth Lowland; but the catchment area and aquifer include a huge spread of Chalk to the North of the Portland and Purbeck Formations..

I tried to obtain permission to dig the spring back in the 1980s or 90s - my interest partly piqued by helping a friend restore to working order the mill a short distance downstream. My request was declined from fears as much of harming the adjacent trout hatchery, as the tourist attraction itself. The owner explained that even the natural sediment after storms can distress the fry.

The spring is very responsive. So much so that daily operations of the Friar Wadden borehole pumps about a mile up-valley were creating sudden rises enough to break the hardwood "cogs"* of the mill gearing, costing more than £10 each. We devised a simple diverter to cast the extra water harmlessly over the weir.

.
* "Cogs" : mill gear teeth. Toothed gears as such are not "cogs"! So now you know.

 

[mrodoc]

Rampisham hill is on the Chalk, so the scope for significant cave development is likely to be rather limited. But interesting from a hydrogeology perspective. Lots of good springs at the base of the chalk at the contact with the Upper Greensand, but I would very much doubt they would be worth digging. Can't see any obvious stream sinks though.

British Geological Survey (BGS) | large image viewer | IIPMooViewer 2.0

largeimages.bgs.ac.uk

Further to the south there is a significant cave at Walditch just outside Bridport. There is a description in an old Descent. It ends in a boulder choke but has walking sized passage and extends at least 50 metres.

 

[richardg]

http://www.mcra.org.uk/registry/sitedetails.php?id=2685 Is this the cave Pete?

 

[richardg]

https://www.mcra.org.uk/surveys/Portland/Walditch Cave.png Here is a map of the cave you mention ?

 

[tim.rose2]

I'm sure Pete won't mind me jumping in first - yes that's the one. I've visited it a couple times in the last few years so can probably answer any questions you have. Beyond the choke the passage is an impressive size (for a non-cave region).
Tim