Mapping Mountains – Hill Reclassifications – Y Pedwarau – The 400m Hills of Wales

Cefn Gwenffrwd (SN 740 486) – 400m Sub-Pedwar reclassified to Pedwar

There has been a reclassification to the listing of the Y Pedwarau – The 400m Hills of Wales, with the summit height, bwlch height and their locations, the drop and status of the hill derived from detail produced by Joe Nuttall in his surface analysis progamme, with subsequent LIDAR analysis conducted by the DoBIH team and independently by Aled Williams and Myrddyn Phillips. 

LIDAR image of Cefn Gwenffrwd (SN 740 486)

The criteria for the list that this reclassification applies to are:

Y Pedwarau – The 400m Hills of Wales.  Welsh hills at or above 400m and below 500m in height that have 30m minimum drop, accompanying the main Y Pedwarau list are five categories of sub hills, with this hill being reclassified from the 400m Sub-Pedwar category.  The criteria for this sub category being all Welsh hills at or above 400m and below 500m in height that have 20m or more and below 30m of drop.  The list is co-authored by Myrddyn Phillips and Aled Williams and is published on Mapping Mountains in Google Doc format.

Y Pedwarau - The 400m Hills of Wales by Myrddyn Phillips and Aled Williams

The name the hill is listed by is Cefn Gwenffrwd and it is adjoined to the Esgair Wen group of hills, which are situated in the central part of South Wales (Region B, Sub-Region B1), and it is positioned with a minor road to its north and south, and has the village of Llanddewibrefi towards the north-west.

When the original 400m height band of Welsh P30 hills was published on Geoff Crowder’s v-g.me website, this hill was included in the accompanying Hills to be surveyed sub list, as it was considered not to meet the criteria then used for the main P30 list.

After the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-evaluated and it was listed with an estimated c 26m of drop, based on the 422m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 396m bwlch height based on interpolation of 10m contouring between 390m – 400m. 

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

When the 1^st edition of the Y Pedwarau was published by Europeaklist in May 2013, the details for this ill were re-evaluated and it was listed as a 400m Sub-Pedwar with 29m of drop, based on the 422m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and the 393m bwlch spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map.

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 reclassification of this hill from 400m Sub-Pedwar status is due to LIDAR analysis, resulting in a 422.7m summit height and a 392.4m bwlch height, with these values giving this hill 30.3m of drop, which is sufficient for it to be classified as a Pedwar. 

 

The full details for the hill are:

Group:  Esgair Wen 

Name:  Cefn Gwenffrwd 

OS 1:50,000 map:  146, 147

Summit Height:  422.7m (LIDAR) 

Summit Grid Reference:  SN 74078 48615 (LIDAR) 

Bwlch Height:  392.4m (LIDAR) 

Bwlch Grid Reference:  SN 74312 49157 (LIDAR) 

Drop:  30.3m (LIDAR)

 

For the additions, reclassifications and deletions to Y Pedwarau – The 400m Hills of Wales reported on Mapping Mountains since the May 2013 publication of the list by Europeaklist please consult the following Change Registers:

 

Y Pedwarau

 

Y Pedwarau – 400m Sub-Pedwarau

 

Y Pedwarau – 390m Sub-Pedwarau

 

Y Pedwarau – 390m Double Sub-Pedwarau

 

Myrddyn Phillips and Aled Williams (July 2023)