Mapping Mountains – Hill Reclassifications – Y Pedwarau – The 400m Hills of Wales

 

Allt y Moch (SO 022 849) – 400m Sub-Pedwar reclassified to Pedwar

There has been a reclassification to the listing of the Y Pedwarau – The 400m Hills of Wales, with the summit height, bwlch height and their locations, the drop and status of the hill confirmed by a Trimble GeoXH 6000 survey conducted by Myrddyn Phillips and Aled Williams, which was prompted by detail produced by Joe Nuttall’s summit analysis programme and subsequent evaluation conducted by Ronnie Bowron. 

Allt y Moch (SO 022 849)

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

Y Pedwarau – The 400m Hills of Wales.  Welsh hills at or above 400m and below 500m in height that have 30m minimum drop, accompanying the main Y Pedwarau list are five categories of sub hills, with this hill being reclassified from the 400m Sub-Pedwar category.  The criteria for this sub category being all Welsh hills at or above 400m and below 500m in height that have 20m or more and below 30m of drop.  The list is co-authored by Myrddyn Phillips and Aled Williams and is published on Mapping Mountains in Google Doc format.

Y Pedwarau - The 400m Hills of Wales by Myrddyn Phillips and Aled Williams

The name the hill is listed by is Allt y Moch and it is adjoined to the Pegwn Mawr group of hills which are situated in Mid and West Wales (Region B, Sub-Region B1), and it is positioned with a minor dead end road to its south and the A470 road to its north-west, and has the village of Llandinam towards the north. 

When the original 400m height band of Welsh P30 hills was published on Geoff Crowder’s v-g.me website this hill was included in the accompanying Hills to be surveyed sub list as it had been surveyed using a basic levelling staff by Myrddyn Phillips on the 18^th August 2003 as having 96½ft / 29.4m of drop. 

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

The evaluation by Ronnie Bowron of the detail produced by Joe Nuttall’s summit analysis programme prompted this hill’s details to be re-assessed via the mapping on the OS Maps website.  This is the replacement for OS Get-a-map and had contours at 5m intervals which were proving consistently more accurate compared to the 5m contours that sometimes appear on Ordnance Survey 1:25,000 Explorer maps and used to appear on the online Vector Map Local.  The bwlch contours on this mapping were between 385m – 390m, therefore if the 421m summit spot height was accurate it meant this hill had at least 30m of drop and would qualify for Pedwar status.  Because of this it was prioritised for a Trimble GeoXH 6000 survey. 

Allt y Moch was surveyed over two days; 11^th July 2020 and 18^th October 2020, with seven data sets taken at the area of its bwlch and six data sets taken at the area of its summit, resulting in the hill now being listed with 30.1m of drop. 

The Trimble GeoXH 6000 gathering data at the bwlch of Allt y Moch

The Trimble GeoXH 6000 gathering data at the summit of Allt y Moch

Therefore, the reclassification of this hill from 400m Sub-Pedwar status is due to a Trimble GeoXH 6000 survey resulting in a 419.7m summit height and a 389.6m bwlch height, with these values giving this hill 30.1m of drop, which is sufficient for it to be classified as a Pedwar. 

 

The full details for the hill are:

Group:  Pegwn Mawr 

Name:  Allt y Moch 

OS 1:50,000 map:  136

Summit Height:  419.7m (converted to OSGM15) 

Summit Grid Reference:  SO 02202 84938 

Bwlch Height:  389.6m (converted to OSGM15) 

Bwlch Grid Reference:  SO 02366 84827 

Drop:  30.1m

 

For the additions, reclassifications and deletions to Y Pedwarau – The 400m Hills of Wales 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

 

Myrddyn Phillips and Aled Williams (October 2020)