Monday 27 July 2020

Mapping Mountains – Significant Name Changes – 30-99m Twmpau and Y Trechol – The Dominant Hills of Wales


Coed Rhedyn (ST 363 893)

There has been a Significant Name Change to a hill that is listed in the 30-99m Twmpau and 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 Coed Rhedyn (ST 363 893)

The criteria for the two listings that this name change 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 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 3rd December 2015, and which is now available in its entirety on Mapping Mountains in Google Doc format.

The hill 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 A48 road to its west and the M4 motorway to its north, and has the city of Casnewydd (Newport) towards the west south-west.

The hill appeared in the original 30-99m Welsh P30 list on Geoff Crowder’s v-g.me website under a partly transposed and invented name of Pen Coed Rhedyn, with an accompanying note stating; Name from wood to the West. 


Pen Coed Rhedyn81mST364893171152Name from wood to the West


During my early hill listing I thought it appropriate to either invent a name for a hill, or use a name that appeared near to the summit of the hill on Ordnance Survey maps of the day.  My preference was to use farm names and put Pen, Bryn or Moel in front of them or as in this instance transpose the name of a wood and add the word Pen to it.  This is not a practice that I now advocate as with time and inclination place-name data can be improved either by asking local people or by examining historic documents, through this form of research an appropriate name for the hill can usually be found.

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

As the summit position indicated by LIDAR is to woodland that comprises a part of Coed Rhedyn and as this is the main named feature of this hill, this name is appropriate to use for the hill and therefore adding an invented name to it is unnecessary.

Therefore, the name this hill is now listed by in the 30-99m Twmpau and Y Trechol – The Dominant Hills of Wales is Coed Rhedyn, and this was derived from the contemporary Ordnance Survey 1:25,000 Explorer map.


The full details for the hill are:

Group:  Gwent Is Coed

Name:  Coed Rhedyn

Previously Listed Name:  Pen Coed Rhedyn

OS 1:50,000 map:  171

Summit Height:  81.3m (LIDAR)

Summit Grid Reference:  ST 36387 89346 (LIDAR)

Bwlch Height:  38.3m (LIDAR)

Bwlch Grid Reference:  ST 36089 89668 (LIDAR) 

Drop:  43.0m (LIDAR)

Dominance:  52.87% (LIDAR)


Myrddyn Phillips (July 2020)






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