Mapping Mountains – Hill Reclassifications – Y Trichant

Bryn Hafod y Llan (SH 945 531) – Sub-Trichant addition

There has been an addition of a hill to the list of the Y Trichant, with the summit height, bwlch height and their locations, the drop and status of the hill confirmed by LIDAR analysis initially conducted by Aled Williams and subsequently by Myrddyn Phillips.

LIDAR image of Bryn Hafod y Llan (SH 945 531)

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

Y Trichant – 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 13^th May 2017.

The name of the hill is Bryn Hafod y Llan, and it is adjoined to the Mynydd Hiraethog group of hills, which are situated in the north-eastern part of North Wales (Region A, Sub-Region A2), and it is positioned with the A5 road to its south and the B4501 road to its east, and has the Alwen Reservoir to the north-east and the village of Cerrigydrudion towards the south. 

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 did not meet the criteria then used for this sub category. 

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

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 18m of drop, based on an estimated summit height of c 397m and a bwlch height of 379m that appears as a spot height on the Ordnance Survey Vector Map Local hosted on the Geograph website and which is entitled the Interactive Coverage Map.

Extract from the Ordnance Survey Vector Map Local hosted on the Geograph website

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. 

The addition of Bryn Hafod y Llan to Sub-Trichant status is due to LIDAR analysis, resulting in a 398.7m summit height and a 378.5m bwlch height, with these values giving this hill 20.1m of drop which is sufficient for it to be classified as a Sub-Trichant.

The full details for the hill are:

Group:  Mynydd Hiraethog

Name:  Bryn Hafod y Llan

OS 1:50,000 map:  116

Summit Height:  398.7m (LIDAR)

Summit Grid Reference:  SH 94590 53115 (LIDAR)

Bwlch Height:  378.5m (LIDAR)

Bwlch Grid Reference:  SH 94564 52682 (LIDAR)

Drop:  20.1m (LIDAR)

Myrddyn Phillips (September 2019)