Mapping Mountains – Hill Reclassifications – Y Trichant – The 300m Hills of Wales and 200m Twmpau

 

Cefn Coch (SN 747 962) – Sub-Trichant reclassified to 200m Sub-Twmpau

There has been a reclassification to the list of Y Trichant – The 300m Hills of Wales and the 200m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived by LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Cefn Coch (SN 747 962)

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

Y Trichant – The 300m Hills of Wales – Welsh hills at or above 300m and below 400m in height that have 30m minimum drop, with an accompanying sub list entitled the Sub-Trichant, with the criteria for this sub category being all Welsh hills at or above 300m and below 400m in height with 20m or more and below 30m of drop.  The list is authored by Myrddyn Phillips with the Introduction to the list and the renaming of it appearing on Mapping Mountains on the 13^th May 2017, and the Introduction to the Mapping Mountains publication of the list appearing on the 1^st January 2022. 

Y Trichant - The 300m Hills of Wales by Myrddyn Phillips

200m Twmpau – Welsh hills at or above 200m and below 300m in height that have 30m minimum drop, with an accompanying sub list entitled the 200m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 200m and below 300m 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.

The 200m Twmpau by Myrddyn Phillips

The name the hill is listed by is Cefn Coch, and it is adjoined to the Banc Llechwedd Mawr group of hills which are situated in the northern part of South Wales (Region B, Sub-Region B1), and it is positioned with the A487 road to its west and a minor roads to its east, and has the town of Machynlleth towards the north.

When the original 300m height band of Welsh P30 hills was published on Geoff Crowder’s v-g.me website, this hill was included in the Hills to be surveyed sub list with an estimated summit height of c 300m based on interpolation of the uppermost ring contour that appears on the Ordnance Survey 1:25,000 Explorer map, with an accompanying note stating; Three points of same height, indicating three separate 300m ring contours. 

Extract from the Ordnance Survey 1:25,000 Explorer map

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales.

Therefore, the reclassification of this hill is due to LIDAR analysis, resulting in 24.6m of drop, with a 299.7m summit height and a 275.1m bwlch height.  Therefore, as the summit height is insufficient for Sub-Trichant status the hill is reclassified to a 200m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Banc Llechwedd Mawr 

Name:  Cefn Coch 

OS 1:50,000 map:  135

Summit Height:  299.7m (LIDAR)                                                           

Summit Grid Reference:  SN 74725 96284 (LIDAR) 

Bwlch Height:  275.1m (LIDAR) 

Bwlch Grid Reference:  SN 75003 95681 (LIDAR) 

Drop:  24.6m (LIDAR) 

 

Myrddyn Phillips (December 2022)