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

Wilcrick Hill (ST 411 878) – Lesser Dominant reclassified to Dominant

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

LIDAR image of Wilcrick Hill (ST 411 878)

The criteria for the list that this reclassification 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 listed by is Wilcrick Hill and it is adjoined to the Gwent Is Coed group of hills which are situated in the south-eastern part of South Wales (Region C, Sub-Region C3), and it is positioned with the B4245 road and the M4 motorway to its north and the A4810 road to its south, and has the city of Casnewydd (Newport) towards the west.

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 34m of drop, based on the 69m summit spot height and the 35m bwlch spot height that appear on the Ordnance Survey 1:25,000 Explorer map.  These values were subsequently used when the Y Trechol – The Dominant Hills of Wales list was first compiled and the hill was listed with 49.28% dominance.

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

As the bwlch contouring represented on the Ordnance Survey 1:25,000 Explorer map is between 30m – 35m with the 35m spot height positioned on a road, the drop value for this hill was re-assessed, resulting in an interpolated height of c 33m for its bwlch being used, and this new value gave this hill a drop value of c 36m and 52.17% dominance and resulted in its reclassification to Dominant status.

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 confirmation of the reclassification of this hill from Lesser Dominant status is due to LIDAR analysis, resulting in a 69.8m summit height and a 33.3m bwlch height, with these values giving this hill 36.4m of drop and 52.21% dominance, which is sufficient for it to be classified as a Dominant hill.

The full details for the hill are:

Group:  Gwent Is Coed

Name:  Wilcrick Hill

OS 1:50,000 map:  171, 172

Summit Grid Reference:  ST 41128 87829 (LIDAR)

Summit Height:  69.8m (LIDAR)

Bwlch Grid Reference:  ST 41353 88003 (LIDAR)

Drop Summit to Bwlch:  36.4m (LIDAR)

Drop Bwlch to ODN:  33.3m (LIDAR)

Dominance:  52.21% (LIDAR)

Myrddyn Phillips (September 2020)