Mapping Mountains – Hill Reclassifications – Y Trichant – The 300m Hills of Wales

Yr Arddu (SH 626 462) – Sub-Trichant addition

There has been an addition to the list of Y Trichant – The 300m Hills of Wales, with the summit height, bwlch height and their locations, the drop and status of the hill derived from spot heights on contemporary Ordnance Survey maps.

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

Y Trichant – The 300m Hills of Wales – Welsh hills at or above 300m and below 400m in height that have 30m minimum drop, with an accompanying sub list entitled the Sub-Trichant with the criteria for this sub category being all Welsh hills at or above 300m and below 400m in height with 20m or more and below 30m of drop.  The list is authored by Myrddyn Phillips, with the Introduction to the list and the renaming of it appearing on Mapping Mountains on the 13th May 2017.

The name the hill is listed by is Yr Arddu, and it is adjoined to the Moelwynion group of hills which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned with the A498 road to its north-west and the A4085 road to its south-west, and has the village of Beddgelert towards the west north-west.

When the original 300m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website this hill was not included in the Hills to be surveyed sub list that accompanied the main P30 list, as it was considered not to meet the criteria then used for this sub category. 

When 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 389m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger map and an estimated bwlch height of c 363m based on interpolation of 10m contouring between 360m – 370m.

Extract from the Ordnance Survey 1:50,000 Landranger map

The details for this hill were re-assessed when the Ordnance Survey Vector Map Local hosted on the Geograph website and which is entitled the Interactive Coverage Map became available online.  This mapping had many spot heights not on other publicly available Ordnance Survey maps and included a 362m spot height on the area of this hill’s bwlch.  This spot height is also shown on Ordnance Survey data that appears on the Magic Maps website. 

Extract from the Magic Maps website

Therefore, the addition of this hill to Sub-Trichant status is due to spot heights on contemporary Ordnance Survey maps, resulting in a 389m summit height and a 362m bwlch height, with these values giving this hill 27m of drop which is sufficient for it to be classified as a Sub-Trichant.

The full details for the hill are:

Group:  Moelwynion

Name:  Yr Arddu

OS 1:50,000 map:  115

Summit Height:  389m (spot height)

Summit Grid Reference:  SH 62652 46230 (spot height)

Bwlch Height:  362m (spot height)

Bwlch Grid Reference:  SH 62863 46313 (spot height)

Drop:  27m (spot heights)

Myrddyn Phillips (February 2020)