Mapping Mountains – Hill Reclassifications – Y Pedwarau

Mynydd yr Ychen (SN 768 794) – 400m Sub-Pedwar reinstated

There has been a hill reinstated to the listing of Y Pedwarau due to 1m DSM LIDAR analysis conducted by Aled Williams.  Y Pedwarau is the title for the list of 400m hills of Wales and takes in all Welsh hills at or above 400m and below 500m in height that have a minimum 30m of drop, the list is a joint compilation between Myrddyn Phillips and Aled Williams and it commenced publication on Mapping Mountains on the 30.01.17.

Accompanying the main Y Pedwarau list are five categories of sub hills, with this hill being reinstated to the 400m Sub-Pedwar category.  The criteria for 400m Sub-Pedwar status is all Welsh hills at or above 400m and below 500m in height with 20m or more and below 30m of drop.

The hill was listed as a 400m Sub-Pedwar with c 20m of drop based on the 459m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated bwlch height of c 439m based on interpolation of bwlch contouring between 430m – 440m.

The hill was then deleted from the ranks of 400m Sub-Pedwarau based on DTM LIDAR analysis which gave a summit height of 459.84m at SN 76846 79457 and a bwlch height of 439.86m at SN 77051 79549, with these values giving this hill 19.98m of drop.

The hill is situated in the Elenydd range with its Cardinal Hill being Draws Drum (SN 790 811) and is placed in the Region of Mid and West Wales (Region B, Sub-Region B2), and is positioned with the small community of Pontarfynach (Devil’s Bridge) to the south-west and Ponterwyd to the north-west.

The hill is a part of designated open access land and can be approached directly from the A 4120 and B 4343 roads which are to the west of the summit, public footpaths also give access to the open access land and originate towards the north-west and the west respectively, otherwise if wanting to visit the hill a longer route can be devised that takes in a number of adjacent hills.

The name the hill is listed by is Mynydd yr Ychen and its reinstatement as a 400m Sub-Pedwar is due to 1m DSM LIDAR analysis conducted by Aled Willams.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales.

The 1m DSM LIDAR analysis gives the hill the following details:

Mynydd yr Ychen

Summit Height:  459.92m

Summit Grid Reference:  SN 76846 79456

Bwlch Height:  439.92m

Bwlch Grid Reference:  SN 77052 79547

Drop:  20.00m

1m DSM LIDAR image of Mynydd yr Ychen

Therefore, the 459.9m 1m DSM LIDAR analysis for the summit position at SN 76846 79456 and the 439.9m 1m DSM LIDAR analysis for the bwlch position at SN 77052 79547 gives this hill 20.0m of drop which is sufficient for it to be reinstated as a 400m Sub-Pedwar.

The full details for the hill are:

Cardinal Hill:  Draws Drum

Summit Height:  459.9m (LIDAR)

Name:  Mynydd yr Ychen

OS 1:50,000 map:  135, 147

Summit Grid Reference:  SN 76846 79456

Drop:  20.0m (LIDAR)

For the additions, reclassifications and deletions to the Y Pedwarau reported on Mapping Mountains since the May 2013 publication of the 1^st edition 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 2018)