Mapping Mountains – Hill Reclassifications – Y Trechol – The Dominant Hills of Wales

 

Rhos Trebared (SN 173 475) – Lesser Dominant deletion

There has been a deletion to the list of the Y Trechol – The Dominant Hills of Wales, with the summit height, bwlch height and their locations, the drop, dominance and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Rhos Trebared (SN 173 475)

The criteria for the list that this deletion applies to are:

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 additional Welsh P30 hills whose prominence is between one third and half that of their absolute height.  The list is authored by Myrddyn Phillips with the Introduction to the start of the Mapping Mountains publication of this list appearing on the 3^rd December 2015, and the list is now available in its entirety on Mapping Mountains in Google Doc format. 

Y Trechol - The Dominant Hills of Wales by Myrddyn Phillips

The name the hill is now listed by is Rhos Trebared and this was derived from local enquiry, and it is adjoined to the Mynydd Bach group of hills, which are situated in the western part of South Wales (Region B, Sub-Region B1), and it is positioned with the coast to its north-west, the B4548 road to its north-east and a minor road to its south, and has the town of Aberteifi (Cardigan) towards the south.

When the original 30-99m height band of Welsh P30 hills published on Geoff Crowder’s v-g.me website were standardised and interpolated heights and drop values also included, this hill was listed with 30m of drop and 43.48% dominance, based on the 69m summit spot height and the 39m bwlch spot height that appear on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map. 

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 deletion of this hill from Lesser Dominant status is due to LIDAR analysis, resulting in a 70.3m summit height and a 40.3m bwlch height, with these values giving this hill 29.9m of drop, which is insufficient for this hill to be classified as a Lesser Dominant. 

 

The full details for the hill are:

Group:  Mynydd Bach

Name:  Rhos Trebared

OS 1:50,000 map:  145

Summit Height:  70.3m (LIDAR)

Summit Grid Reference:  SN 17391 47521 (LIDAR)

Bwlch Height:  40.3m (LIDAR)

Bwlch Grid Reference:  SN 17728 47659 (LIDAR)

Drop:  29.9m (LIDAR)

Dominance:  drop insufficient for qualification

 

Myrddyn Phillips (February 2023)