Mapping Mountains – Summit Relocations – 30-99m Twmpau and Y Trechol – The Dominant Hills of Wales

Broughton Burrows (SS 413 927)

There has been a Summit Relocation to a hill that is listed in the 30-99m Twmpau and Y Trechol – The Dominant Hills of Wales, with the summit height and drop of the hill being confirmed by LIDAR analysis conducted by Myrddyn Phillips.

LIDAR image of Broughton Burrows

The criteria for the two lists that this summit relocation applies to are:

30-99m Twmpau - Welsh hills at or above 30m and below 100m in height with 30m minimum drop, with an accompanying sub list entitled the 30-99m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 30m and below 100m 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.

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 addition Welsh P30 hills whose prominence is 33.33% or more and below 50% 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.

LIDAR image of Broughton Burrows showing the summit and connecting bwlch

The name of the hill is Broughton Burrows, and it is adjoined to the Gŵyr group of hills, which are situated in the western part of South Wales (Region C, Sub-Region C1), and it is positioned at the western end of the Gŵyr, and has the small community of Llangynydd towards the south-east.

Although the summit of this hill is not a part of open access land, and as such permission to visit should be sought, there is general acceptance for people to visit, with the nearest public footpath encircling the summit of the hill which comprises a dune system.

Close up LIDAR summit image of Broughton Burrows

Prior to LIDAR analysis and the inspection of 5m contouring on OS Maps, which is the recent replacement for OS Get-a-map, this hill was listed with c 32m of drop and 65.31% dominance based on the 49m spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an interpolated bwlch height of c 17m based on what was thought to be bwlch contouring between 15m – 20m.  However, as this hill is a part of a dune system this map did not show continuous contours on either the summit or bwlch area of this hill.

Extract from OS Maps

The summit height produced by LIDAR analysis is 61.9m at SS 41391 92781 and its position in relation to that previously given comes within the parameters of the Summit Relocations used within this page heading, these parameters are:

The term Summit Relocations applies to any listed hill whose summit meets the following criteria; where there are a number of potential summit positions within close proximity and the highest point is not where previously given, or a relocation of approximately 100 metres or more in distance from either the position of a map spot height or from where the summit of the hill was previously thought to exist, or when the summit of the hill is in a different field compared to where previously given, or when the natural and intact summit of a hill is confirmed compared to a higher point such as a raised field boundary that is judged to be a relatively recent man-made construct.  As heights on different scaled Ordnance Survey maps are not consistent the height given on the 1:25,000 Explorer map is being prioritised in favour of the 1:50,000 Landranger map for detailing these relocations.

The summit height produced by LIDAR analysis is 61.9m and is positioned at SS 41391 92781, this position is not given a spot height on contemporary Ordnance Survey maps and is approximately 450 metres south-east from where the 49m spot height appears on the Ordnance Survey 1:25,000 Explorer map.  

The Ordnnance Survey Interactive Coverage map hosted on the Geograph website showing the summit position in relation to where the 49m spot height appears

 

The full details for the hill are:

Group:  Gŵyr

Name:  Broughton Burrows

OS 1:50,000 map:  159

Summit Height:  61.9m (LIDAR)

Summit Grid Reference (new position):  SS 41391 92781 (LIDAR)

Bwlch Height:  17.4m (LIDAR)

Bwlch Grid Reference:  SS 41739 92663 (LIDAR)

  

Drop:  44.5m (LIDAR)

Dominance:  71.95% (LIDAR)

Myrddyn Phillips (December 2018)