Mapping Mountains – Significant Name Changes – 100m Twmpau and Y Trechol – The Dominant Hills of Wales

Clytiau Poethion (SH 763 717)

There has been a Significant Name Change to a hill that is now listed in the 100m Twmpau and Y Trechol – The Dominant Hills of Wales, with the summit height and its location, the drop and status of the hill confirmed by LIDAR analysis and its summit height subsequently confirmed by a Trimble GeoXH 6000 survey, both conducted by Myrddyn Phillips, with the latter taking place on the 10^th October 2018.

LIDAR image of Clytiau Poethion (SH 763 717)

The criteria for the two lists that this name change applies to are:

100m Twmpau - Welsh hills at or above 100m and below 200m in height with 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m 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.

Y Trechol – The Dominant Hills of Wales – Welsh P30 hills whose prominence equal or exceed half that of their absolute height.  With the criteria for Lesser Dominant status being those additional Welsh P30 hills whose prominence is between one third and half that of their absolute height.  The list is authored by Myrddyn Phillips with the Introduction to the start of the Mapping Mountains publication of this list appearing on the 3^rd December 2015.

The hill is adjoined to the Carneddau group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is encircled by minor roads with the B5106 and the Afon Conwy (River Conwy) to its east, and has the town of Conwy to its north.

The hill has not previously been listed as its adjacent northerly hill of Maes Glas Mawr (SH 76876 72414) was thought to be higher, LIDAR analysis and the survey with the Trimble GeoXH 6000 proved otherwise and therefore Clytiau Poethion is now listed as the 100m Twmpau and the Lesser Dominant hill.

As the summit of this hill comprises bounded land the details for it were examined on the Tithe map.  The term Tithe map is generally given to a map of a Welsh or English parish or township and which was prepared after the 1836 Tithe Commutation Act.  This act allowed tithes to be paid in cash rather than goods.  The Tithe maps gave names of owners and occupiers of land in each parish and importantly for place-name research they also included the name of enclosed land.  This enclosed land is usually based on a field system, however not every field is given a name, but many are and especially so in Wales.

Extract from the Tithe map

The enclosed land where the summit of this hill is situated is given the number 195 on the Tithe map, this can be cross referenced against the apportionments; it is these apportionments that give the name of the owner or occupier of the land as well as the name of the land.  The land where the summit of this hill is situated is named as Clylliau [sic] Poethion in the apportionments, with the details on the Tithe map appearing in the parish of Caerhun and in the county named as Caernarvonshire [sic].

Extract from the apportionments

Therefore, the name this hill is now listed by in the 100m Twmpau and Y Trechol – The Dominant Hills of Wales is Clytiau Poethion, and this name was derived from the Tithe map.

The full details for the hill are:

Group:  Carneddau

Name:  Clytiau Poethion

Previously Listed Name:  not previously listed 

OS 1:50,000 map:  115

Summit Height:  109.1m (converted to OSGM15)

Summit Grid Reference:  SH 76337 71799

Bwlch Height:  68.7m (LIDAR)

Bwlch Grid Reference:  SH 77496 72493 (LIDAR)

 

Drop:  40.35m (Trimble summit and LIDAR bwlch)

Dominance:  37.00% (Trimble summit and LIDAR bwlch)

For details of the summit survey of this hill

Myrddyn Phillips (March 2019)