Mapping Mountains – Hill Reclassifications – Y Pedwarau

Fynach Fawr (SN 726 890) – 400m Sub-Pedwar reinstated to Pedwar

There has been a reclassification to the listing of Y Pedwarau due to a survey with the Trimble GeoXH 6000 which took place on the 03.06.18, coupled with LIDAR analysis.  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 reclassified from a 400m Sub-Pedwar to a Pedwar.  The criteria for 400m Sub-Pedwar status is all Welsh hills at or above 400m and below 500m in height that have 20m or more and below 30m of drop.

The name of the hill is Fynach Fawr and prior to the Trimble GeoXH 6000 survey it was listed with 28.9m of drop, based on LIDAR analysis giving a 461.4m summit and 432.5m bwlch height, resulting in Fynach Fawr being reclassified to a 400m Sub-Pedwar.  This hill was then re-analysed via LIDAR by Chris Crocker resulting in a different conclusion, therefore the DSM LIDAR model was re-analysed with the conclusion being that LIDAR could not safely ascertain whether this hill was a Pedwar, and therefore the Trimble GeoXH 6000 survey was conducted in an attempt to confirm the status of this hill, resulting in the classification of this hill reversing to pre LIDAR analysis.

The hill is a part of the Pumlumon range with its Cardinal Hill being Banc Llechwedd Mawr (SN 775 898) and is placed in the Region of Mid and West Wales (Region B, Sub-Region B2).  The hill is situated with the Nant y Moch Reservoir to its south-east, and has the small community of Tal-y-bont towards the west.

 

Fynach Fawr (SN 726 890)

Although the hill is a part of designated open access land it is also immersed in conifer plantation.  However, the summit of the hill is relatively easy to reach from the convenience of a forest track to its north north-east.

The survey with the Trimble GeoXH 6000 resulted in a summit height of 462.5m, and with a bwlch height of 432.5m from LIDAR analysis, these values give this hill 30.0m of drop, which is sufficient for its reinstatement to Pedwar status.

 

The full details for the hill are:

Cardinal Hill:  Banc Llechwedd Mawr

Name:  Fynach Fawr

OS 1:50,000 map:  135

Summit Height:  462.5m (converted to OSGM15)

Summit Grid Reference:  SN 72685 89095

Bwlch Height:  432.5m (LIDAR)

Bwlch Grid Reference:  SN 72911 89413 (LIDAR) 

   

Drop:  30.0m (Trimble summit and LIDAR bwlch)

 

The Trimble GeoXH 6000 set-up position at the summit of Fynach Fawr

For the additions, reclassifications and deletions to Y Pedwarau 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

Our thanks to Chris Crocker for suggesting that the data produced by LIDAR be re-evaluated for this hill, and to Mick Moore for a helpful and detailed synopsis of his route to this hill’s summit

For details relating to the survey of Fynach Fawr

Myrddyn Phillips and Aled Williams (September 2018)