Mapping Mountains – Significant Name Changes – 100m Twmpau and Y Trechol – The Dominant Hills of Wales

Rhiw Las (SN 318 545) 

There has been a Significant Name Change to a hill that is listed in the 100m 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 derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Rhiw Las (SN 318 545)

The criteria for the two listings that this name change applies to are:

100m Twmpau – Welsh hills at or above 100m and below 200m in height that have 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau, with the criteria for this sub category being all Welsh hills at or above 100m and below 200m 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. 

The 100m Twmpau by Myrddyn Phillips

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 hill 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 and west, and the B4321 road to its south, and has the village of Llangrannog towards the south.

The hill appeared in the original Welsh 100m P30 list on Geoff Crowder’s v-g.me website, under the transposed name of Allt y Cwrt, which is a prominent name that appears to the east of this hill on the contemporary Ordnance Survey 1:25,000 Explorer map.

Allt y Cwrt

167m

SN318545

145

198

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 a name that appeared on the Ordnance Survey 1:25,000 Explorer map and presume it that of the hill.  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

There are a number of books specialising in the place-names of Wales.  Many are recommended as they give a historical context to the names we still use.  The names that relate to hills originate from the local community and although many do not appear on Ordnance Survey maps they have as much integrity as those that do. 

For the name of this hill it is the three volume set written and researched by Iwan Wmffre that gives the name of this hill as Rhiw Las.  The books are entitled The Place-Names of Cardiganshire and they are published by the British Archaeological Reports Oxford Ltd. 

Therefore, the name this hill is now listed by in the 100m Twmpau and Y Trechol – The Dominant Hills of Wales is Rhiw Las, and this was derived from the book entitled The Place-Names of Cardiganshire which is authored by Iwan Wmffre.

 

The full details for the hill are:

Group:  Mynydd Bach

Name:  Rhiw Las

Previously Listed Name:  Allt y Cwrt   

OS 1:50,000 map:  145

Summit Height:  167.2m (LIDAR) 

Summit Grid Reference:  SN 31887 54547 (LIDAR) 

Bwlch Height:  99.1m (LIDAR) 

Bwlch Grid Reference:  SN 32903 54487 (LIDAR) 

Drop:  68.1m (LIDAR) 

Dominance:  40.72% (LIDAR)

 

My thanks to Aled Williams for advice in relation to the name of this hill

Myrddyn Phillips (January 2023)