Mapping Mountains – Summit Relocations – 100m Twmpau and Y Trechol – The Dominant Hills of Wales

Allt Cunedda (SN 407 090)

There has been a Summit Relocation to a hill that is listed in the 100m Twmpau and Y Trechol – The Dominant Hills of Wales, with the summit height and position confirmed by LIDAR analysis conducted by Myrddyn Phillips.

LIDAR image of Allt Cunedda with the raised covered reservoir on bottom left and the summit of Allt Cunedda in the centre right

The criteria for the two listings that this summit relocation applies to are:

100m Twmpau - Welsh hills at or above 100m and below 200m in height with 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward.

Y Trechol - The Dominant Hills of Wales - Welsh P30 hills whose prominence  equal or exceed half that of their absolute height.  With the criteria for Lesser Dominant status being those addition Welsh P30 hills whose prominence is 33.3% or more and below 50% of their absolute height, with the Introduction to the Mapping Mountains publication of this list appearing on the 3^rd December 2015.

The name of the hill is Allt Cunedda and it is adjoined to the Mynydd Sylen group of hills, which are situated in the western part of South Wales (Region C, Sub-Region C1), and is positioned with the stream valley of the Gwendraeth Fach and the A 484 road to the east, and has the small town of Cydweli (Kidwelly) towards the south.

As the summit of this hill is not a part of designated open access land permission to visit should be sought, for those wishing to do so the nearest public footpath is to the south of the summit and relatively close to it.

Prior to LIDAR analysis this hill was listed with c 129m of drop based on the 192m summit spot height that is given to a triangulation pillar on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer maps and an estimated bwlch height of c 63m based on interpolation of bwlch contouring between 60m – 65m. 

Extract from the Ordnance Survey Interactive Coverage Map hosted on the Geograph website showing the summit position in relation to the trig pillar spot height position

The triangulation pillar is given a flush bracket height of 192.353m and is positioned at SN 40676 08999 and sits atop a concrete plinth that is approximately 0.15 – 0.2m high, and is positioned on grass at the base of a covered reservoir beside a concrete track giving access from a gate.  The trig pillar seems to have been positioned on the hill before the construction of the covered reservoir and therefore in all likelihood is placed on natural ground.  Therefore, dependent upon the accuracy of the flush bracket, the ground at the base of the trig pillar is approximately 191.8 - 191.9m in height.    

The summit height produced by 1m DTM LIDAR analysis is 192.7m and is positioned at SN 40749 09013, this position is to the remains of a barrow that has been ploughed down to approximately 0.5m in height and which is situated in a field.  This position is not given a spot height on Ordnance Survey maps and is approximately 75 metres east from where the previously listed summit position is situated.

The full details for the hill are:

Group:  Mynydd Sylen

Name:  Allt Cunedda

Summit Height:  192.7m (LIDAR)

OS 1:50,000 map:  159

Summit Grid Reference (New Position):  SN 40749 09013 (LIDAR)

  

Drop:  c 130m

Dominance:  67.30% (LIDAR) 

Myrddyn Phillips (November 2018)