Friday, 25 July 2014

Mapping Mountains – Trimble Surveys – Bannau Brycheiniog


22.07.14  Allt Lwyd (SO 078 189), Waun Rydd (SO 062 206) and Bryn (SO 071 226)


The high Bannau Brycheiniog peaks from the northern slopes of Waun Rydd
After visiting Bryn Melyn (SO 109 184) we drove down to the valley and parked beside the Talybont Reservoir at SO 099 197.  Our original plan was to visit Waun Rydd and Bryn, but a quick examination of the map showed that Allt Lwyd is a Sub-Hewitt and Sub-Sim with an estimated c 28m of drop (once back home I examined the Ordnance Survey enlarged Geograph map, it has a spot height on this hill’s critical bwlch giving it 28m of drop).  Excited with the prospect of potential new Hewittdom we quickly changed our plans and headed toward Allt Lwyd.

Opposite the small pull in area a track can be followed that leads to a gate and a path then heads uphill to a small ladder stile before the open hillside.  Further east the morning’s sunshine was still baking the hills, but our ascent route was now under high cloud cover, even if this helped in lowering the temperature the ascent was still very warm.  I oozed sweat at every step and became absolutely sodden, this and the sometimes high pollen count are two major disadvantages of summer walking, but as height was gained the merest breath of breeze occasionally filtered over the land.  I set a slow but consistent pace and Mark followed a few hundred metres behind.  The land to the east started to appear with the reservoir being foreground to the long ridges of Mynyddoedd Duon.

Looking across Talybont Reservoir toward the elongated ridges of Mynyddoedd Duon
We reached a corner of a forest where I stopped and appreciated the sweep of ridge line between Allt Lwyd and Waun Rydd, the hills of Bannau Brycheiniog portray an architectural shape seldom seen anywhere else in the country as accentuated lines sweep up to truncated summits and then plunge in descending curves down to the next bwlch before ascent lines sweep back up, all repeated time and time again.

The path continues beyond the corner of the forest to the summit of Allt Lwyd, which is behind the trees on the left
Mark on the final bit of up hill leading to the summit of Allt Lwyd
The last part of the ascent is on a good path that led up to the small cairned summit, as Mark sat and enjoyed his lunch looking out toward Waun Rydd I set the Trimble up on the highest bit of land close to the small cairn and gathered ten minutes of data.

Gathering data at the summit of Allt Lwyd
After lunch we descended to the bwlch which is narrow between the valley to valley traverse and elongated between the hills.  We spent a few minutes judging where the critical bwlch was and set the Trimble up for another ten minutes of data collection.  Having had hopes that Allt Lwyd may become a new Sim and Hewitt before the ascent, once we arrived at the bwlch our hopes were somewhat dashed as we both thought the hill looked as if it only had around 25m of drop.  We’ll have to wait until the data is processed to see if our on ground estimation is more accurate than the Ordnance Survey spot heights that give the hill 28m of drop.

Gathering data at the critical bwlch of Allt Lwyd
The connecting ridge leading up to the summit plateau of Waun Rydd is rather slender in shape and sometimes steep, looking behind I focused on Mark as he made his way up with Allt Lwyd framed in the background.  To the west the escarpment edge named Gwalciau’r Cwm on the map was slowly highlighted in a patch of sunshine, a perfect enhancement to its steep sided greens.
 
Allt Lwyd (SO 078 189)
Sunlight on the escarpment edge of Gwalciau'r Cwm
Once the steep ridge is crested a number of paths give options for onward progress, we used the path that headed straight in to the slowly rising moor toward the summit of Waun Rydd.  This hill is not typical of the region as its top is plateau like, whereas other summits are comprised of truncated land of smaller area.  As height was gained on the path the land to our north came in to view and there sat Bryn, our last objective of the day.

Bryn (SO 071 226)
The high point of Waun Rydd has two distinct possibilities for its summit, with a third cairned high point that we thought lower.  Each had five minutes of data gathered from its respective high point, I favoured the most southerly option to be the highest, whilst Mark thought the central option was the true summit.

First (southern) summit option looking toward Mark on the second (central) summit option.  The result for this placement came to 768.411m at SO 06229 20546
Second (central) summit option looking toward the cairn atop the third (northern) summit option.  The result for this placement came to 769.158 at SO 06211 20645
Third (northern) summit option looking toward Mark on the second (central) summit option.  The result for this placement came to 768.541 at SO 06209 20680
On our way down to the last summit of the day; Bryn, the sun broke through as the western cloud bank slowly dispersed.  Looking westward to the higher mountains the sun had cask a metallic gleam mixing blues and grey on their profiles, but just as quickly as the colour feast materialised so did the reoccurrence of overheating with copious amounts of sweat produced in a lost hope of cooling the body.

Mixing blues with grey on the high peaks of Bannau Brycheiniog
Data was gathered at the bwlch of Bryn before we followed a sheep track up to the summit.  The Ordnance survey 1:25,000 map gives a 562m spot height at SO 071 226 and the 1:50,000 map gives a 561m spot height at SO 072 227, the latter position has a cairn on it and views across the flatlands to the north.  Both positions were Trimbled before we headed down the south-eastern flank of the hill toward a forest.

Gathering data at the critical bwlch of Bryn
Waun Rydd (SO 062 206) from the bwlch of Bryn
Gathering data at the high point of Bryn.  The result for this placement came to 561.951m at SO 07132 22696
Gathering data beside the cairn at the second option for the summit of Bryn.  The result for this placement came to 561.206m at SO 07287 22759
Once beside the conifer plantation we assessed our options and decided to head down to a stream crossing and ascend a track on the opposite side.  This descent gave us the last views of Waun Rydd in early evening light, aglow as the sun started to cast long showers.

Heading down the south-eastern flank of Bryn
Waun Rydd bathed in early evening light
The ascent on the opposite side of the stream was evil and I suffered, the track eventually led to one or two farm houses and down on to the lane that in time brought us back to the awaiting car.  This return journey seemed long as I suffered in the sun and plodded uphill on the lane as it headed toward the reservoir dam, here we rested and looked at the reflected colours in the water.  Arriving back at the car was very welcome.  Time to rest and sit down – yummy!!

Doesn't look much, but this last bit of up hill was a wee bit evil
   
 
Tor y Foel above the coloured waters of the Talybont Reservoir


Survey Result:

Allt Lwyd

Summit Height:  653.2m (converted to OSGM15) 
 
Summit Grid Reference:  SO 07860 18909

Bwlch Height:  625.4m (converted to OSGM15)

Bwlch Grid Reference:  SO 07535 19113

Drop:  27.7m  (Sub-Simm, Sub-Hewitt and 600m Sub-Twmpau status confirmed)

Dominance:  4.24%



Waun Rydd

Summit Height:  769.2m (converted to OSGM15)
 
Summit Grid Reference:  SO 06211 20645

Drop:  170m

Dominance:  22.10%



Bryn

Summit Height:  562.0m (converted to OSGM15)
 
Summit Grid Reference:  SO 07132 22696

Bwlch Height:  530.3m (converted to OSGM15)

Bwlch Grid Reference:  SO 06718 22457

Drop:  31.6m  (Dodd, Dewey and 500m Twmpau status confirmed)

Dominance:  5.63%



For further details please consult the Trimble survey spreadsheet click {here}

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