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

No Name Stack (SR 975 932) – Dominant deletion

There has been a deletion to the listing of Y Trechol – The Dominant Hills of Wales due to LIDAR analysis conducted by Myrddyn Phillips, with the criteria for this list being:

Y Trechol – The Dominant Hills of Wales - Welsh P30 hills whose prominence equal or exceed half that of their absolute height.

Prior to LIDAR analysis this hill was listed with 30m of drop based on the 30m spot height that appears on the Ordnance Survey 1:25,000 Explorer map, with the height of the bwlch accepted as that for Ordnance Datum Newlyn (sea level), however map data indicates that this hill is adjoined to the mainland and is not tidal, indicating that its status as a P30 was debatable.

When the original Welsh P30 lists were compiled I contacted Dave Viggers in relation to sea stacks positioned around the Pembrokeshire coast, regarding their height, location and name.  Dave is now a Vice President of the Climber’s Club and gave me invaluable information including the location of this hill, its approximate height and its name, which he advised was known as No Name Stack.

Although the name of this hill implies that it is a sea stack, it is adjoined to the mainland.  The hill is adjoined to the Brandy Hill group of hills, which are situated in the south-western part of Mid and West Wales (Region B, Sub-Region B4), and is positioned with the coast to its immediate south-east and has St Govan’s Head to its south and Broad Haven towards its north north-east, and has the village of Bosherston towards its north-west.

If wanting to visit this hill permission to do so should be sought as it is not a part of designated open access land, for those wishing to do so caution is advised as the easiest approach will necessitate some form of climbing.

The deletion of No Name Stack from Dominant status is due to LIDAR analysis conducted by Myrddyn Phillips.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

LIDAR image of the bwlch of No Name Stack

LIDAR image of the summit of No Name Stack

The 2m DSM LIDAR analysis gives the hill the following details:

Name:  No Name Stack

Summit Height:  31.1m

Summit Grid Reference:  SR 97567 93273

Bwlch Height:  2.6m

Bwlch Grid Reference:  SR 97553 93308

Drop:  28.5m

Dominance:  not applicable as under 30m prominence

Therefore, the 31.1m LIDAR analysis for the summit position at SR 97567 93273 and the 2.6m LIDAR analysis for the bwlch position at SR 97553 93308 gives this hill 28.5m of drop, which is insufficient for Dominant status.

LIDAR image of No Name Stack

The full details for the hill are:

Group:  Brandy Hill

Name:  No Name Stack

Dominance:  not applicable as under 30m prominence

OS 1:50,000 map:  158

Summit Grid Reference:  SR 97567 93273 (LIDAR)

Summit Height:  31.1m (LIDAR)

Bwlch Grid Reference:  SR 97553 93308 (LIDAR)

Drop Summit to Bwlch:  28.5m (LIDAR)

Drop Bwlch to ODN:  2.6m (LIDAR)

Myrddyn Phillips (September 2018)