Mapping Mountains – Significant Name Changes – 30-99m Twmpau

 

Rhos Uchaf (SH 593 699) 

There has been a Significant Name Change to a hill that is listed in the 30-99m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips.

LIDAR image of Rhos Uchaf (SH 593 699)

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

30-99m Twmpau – Welsh hills at or above 30m and below 100m in height that have 30m minimum drop, with an accompanying sub list entitled the 30-99m Sub-Twmpau, with the criteria for this sub category being all Welsh hills at or above 30m and below 100m in height with 20m or more and below 30m of drop.  The list is authored by Myrddyn Phillips, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

30-99m Twmpau by Myrddyn Phillips

The hill is adjoined to the Glyder Fawr 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 A5 road to its immediate west and the A55 road to its south-east, and has the city of Bangor towards the north-west.

When the original 30-99m 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 this hill was still not listed, with its details subsequently documented under the point (Pt. c 93m) notation with an estimated c 16m of drop, based on an estimated c 93m summit height and an estimated c 77m bwlch height, with both heights based on interpolation of 5m contouring. 

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 85 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 Rhos Uchaf in the apportionments, with the details on the Tithe map appearing in the parish named as Llandygái and in the county named as Caernarfon. 

Extract from the apportionments

Therefore, the name this hill is now listed by in the 30-99m Twmpau is Rhos Uchaf, with this was derived from the Tithe map. 

 

The full details for the hill are:

Group:  Glyder Fawr

Name:  Rhos Uchaf

Previously Listed Name:  Pt. c 93m 

OS 1:50,000 map:  114, 115

Summit Height:  92.5m (LIDAR) 

Summit Grid Reference:  SH 59332 69923 (LIDAR)               

Bwlch Height:  71.8m (LIDAR) 

Bwlch Grid Reference:  SH 59236 69468 (LIDAR) 

Drop:  20.7m (LIDAR)

 

Myrddyn Phillips (April 2025)