Mapping Mountains – Hill Reclassifications – 200m Twmpau

 

Foel Fryniau (SH 633 306) – 200m Sub-Twmpau reclassified to 200m Twmpau

There has been a reclassification to the list of 200m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived by Joe Nuttall who produced a summit analysis programme using LIDAR, and then by LIDAR analysis initially conducted by Jim Bloomer and subsequently by Myrddyn Phillips. 

LIDAR image of Foel Fryniau (SH 633 306)

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

200m Twmpau – Welsh hills at or above 200m and below 300m in height that have 30m minimum drop, with an accompanying sub list entitled the 200m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 200m and below 300m 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 200m Twmpau by Myrddyn Phillips

The name the hill is listed by is Foel Fryniau and it is adjoined to the Rhinogydd group of hills, which are situated in the western part of North Wales (Region A, Sub-Region A3), and it has the A496 road to its west and the A470 road to its east, and has the town of Harlech towards the west. 

When the original 200m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website this hill was 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 the main P30 category. 

When the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-assessed and it was listed with an estimated c 26m of drop, based on the 222m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 196m bwlch height, based on interpolation of 10m contouring between 190m – 200m.  When The Welsh P15s list was being compiled the details for this hill were again reassessed and its drop value amended from c 26m to an estimated c 27m. 

Extract from the Ordnance Survey 1:25,000 Explorer 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 200m Sub-Twmpau status is due to LIDAR analysis, resulting in a 221.0m summit height and a 190.2m bwlch height, with these values giving this hill 30.8m of drop, which is sufficient for it to be classified as a 200m Twmpau. 

 

The full details for the hill are: 

Group:  Rhinogydd 

Name:  Foel Fryniau 

OS 1:50,000 map:  124

Summit Height:  221.0m (LIDAR) 

Summit Grid Reference:  SH 63325 30662 (LIDAR) 

Bwlch Height:  190.2m (LIDAR) 

Bwlch Grid Reference:  SH 63515 30647 (LIDAR) 

Drop:  30.8m (LIDAR) 

 

Myrddyn Phillips (March 2021)