Wednesday, 19 April 2017

Mapping Mountains – Hill Reclassifications – Y Trichant


Twyn y Ffald (SN 852 160) - Sub-Trichant addition

There has been an addition to the listing of the Y Trichant, this is the draft title for the hills in the 300m height band of the Twmpau (thirty welsh metre prominences and upward) due to analysis of LIDAR data by Aled Williams.  With the criteria for Y Trichant being all Welsh hills 300m or more and below 400m in height with 30m minimum drop.

Accompanying the main Y Trichant list is a sub list entitled the Sub-Trichant.  With the criteria for Sub-Trichant qualification being all Welsh hills at or above 300m and below 400m in height with 20m or more and below 30m of drop.

Prior to analysis of LIDAR data the hill was catalogued with c 19m of drop which was insufficient for it to be listed as a Sub-Trichant, this drop value was based on an estimated summit height of c 362m and an estimated bwlch height of c 343m, with the latter taken to land that forms a part of a disused quarry, and therefore the old connecting bwlch of this hill no longer exists.

The hill is adjoined to the Fforest Fawr group of hills with its Cardinal Hill being Fan Gyhirych (SN 880 191) and is placed in the Region of South Wales (Region C, Sub-Region C2), and is situated with the small community of Glyntawe to its north-west.

The hill can be accessed from the end of a minor road at Penwyllt and can be combined with higher hills to its east.  However, the summit of this hill is not on open access land and it is positioned on the periphery of a disused quarry, therefore permission should be sought to visit, but with open access land relatively close towards the north-east, common sense should prevail and if wanting to visit the summit there is likely to be no objection to doing so.

The name of the hill is Twyn y Ffald and its addition to Sub-Trichant status is due to analysis of LIDAR data by Aled Williams.  LIDAR (Light Detection & Ranging) is highly accurate height data that is now freely available for much of England and Wales.

Aled’s analysis of LIDAR data gives the hill the following details:


Twyn y Ffald

Summit Height:  368.7m

Summit Grid Reference:  SN 85227 16034

Bwlch Height:  342.8m

Bwlch Grid Reference:  SN 85541 16188

Drop:  25.9m


Therefore, the 368.7m LIDAR data produced for the summit position at SN 85227 16034 and the 342.8m LIDAR data produced for the bwlch position at SN 85541 16188 gives this hill 25.9m of drop, which is sufficient for its inclusion as a Sub-Trichant, therefore this hill is included in this sub category and the total in the Y Trichant and the Twmpau which will be updated accordingly.


The full details for the hill are:

Cardinal Hill:  Fan Gyhirych

Summit Height:  368.7m (LIDAR data)

Name:  Twyn y Ffald

OS 1:50,000 map:  160

Summit Grid Reference:  SN 85227 16034
   
Drop:  25.9m (LIDAR data)



My thanks to Aled Williams for sending the details of this hill to me.



Myrddyn Phillips (April 2017)

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