Mapping Mountains – Significant Name Changes – 100m Twmpau

Bonc y Garreg (SH 486 804) 

There has been a Significant Name Change to a hill that is listed in the 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill confirmed by LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Bonc y Garreg (SH 486 804)

The criteria for the list 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. 

The 100m Twmpau by Myrddyn Phillips

The hill is adjoined to the Ynys Môn group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned with the B5110 road to its west and has a minor road to its south-east, and has the village of Benllech towards the north-east. 

When the original 100m 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, as it was considered not to meet the criteria then used for this sub category. 

After 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 under the point (Pt. 114m) notation with an estimated c 27m of drop, based on the 114m summit spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage map and an estimated c 87m bwlch height based on interpolation of 5m contouring between 85m – 90m that appear on the Ordnance Survey 1:25,000 Explorer map. 

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

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 748 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 Bonc y Garreg in the apportionments, with the details on the Tithe map appearing in the parish of Llanddyfnan and in the county named as Anglesey. 

Extract from the apportionments

Therefore, the name this hill is now listed by in the 100m Twmpau is Bonc y Garreg, and this was derived from the Tithe map. 

 

The full details for the hill are: 

Group:  Ynys Môn 

Name:  Bonc y Garreg

Previously Listed Name:  Pt. 114m 

OS 1:50,000 map:  114, 115

Summit Height:  114.0m (LIDAR) 

Summit Grid Reference:  SH 48627 80418 (LIDAR) 

Bwlch Height:  87.1m (LIDAR) 

Bwlch Grid Reference:  SH 48221 80516 (LIDAR) 

Drop:  26.9m (LIDAR) 

 

Myrddyn Phillips (March 2021)