Hill Lists – Cymru / Wales – 200m Twmpau updates – Bryniau Dyfi

The first list to the Welsh 200m P30 hills was published on Geoff Crowder’s website v-g.me in 2000; this list preceded the list of TuMPs by nine years, the list proved a very useful resource for the TuMP compilation for this category of hill.

The Welsh 200m P30 list documents all hills in Wales that are at or above 200m in height and are below 300m in height, to qualify for the main list each hill requires a minimum of 30m of prominence.

The hills listed below are updates to the Welsh 200m P30 list originally published on Geoff Crowder's website.  To see the original list click {here}

The original published list had a Sub-List which was entitled ‘Hills to Survey’.  This list consisted of all hills in Wales in the stipulated height band that have a minimum of 20m of prominence, but do not meet the minimum 30m of prominence to enter the main list, according to Ordnance Survey map spot heights and contours.  Nowadays the standard Sub-List takes in all hills that have a minimum of 20m of prominence.  However, the Hills to Survey Sub-List discounted hills whose map spot heights gave a drop value of less than 30m, but more than 20m.  By doing so, the only hills that were Sub-Listed were those that map values dictated stood a chance of entering the main list, for example; if a hill had a summit spot height of 250m and a bwlch spot height of 221m, it was not listed in the Hills to Survey Sub-List as with 29m of drop I thought it did not stand a chance of main list qualification. 

When compiling the Sub-List I was measuring many hills for P30 status using a basic levelling technique, please click {here} for more information concerning this.  I now know that Ordnance Survey spot heights have a standard margin of uncertainty of + / - 3m associated with their accuracy.  Therefore many hills that were not listed in the original Sub-List may have sufficient drop to enter the main list.  Because of this the Sub-List has been altered to include all hills that have a minimum of 20m of drop but are not known to attain the minimum 30m of drop to enter the main list.

The hills listed below are those major amendments to the original Welsh 200m P30 list as it appears on Geoff’s website.  There are many hills that have been promoted from the Hills to Survey Sub-List to the main list, whilst there are many additions to the Sub-List now that it has been standardised to include all 20m minimum but below 30m drop hills.

When the 200m P30 list was first published it was the first to this category of hills and in some way it and its other 100m height band lists paved the way for Clem’s data that later appeared on the RHB file database and then for the TuMPs listing by Mark Jackson.

As well as the first P30 list to this height band the list is now the first to include a comprehensive Sub-List.

TuMP baggers beware; as the main list also includes P30’s not listed by Mark Jackson, so if you want to visit all P30’s you’ll have to include some non TuMPs to do so.

The list will be updated on a weekly basis and will be done so through each Group category, starting from the north and working south.  The twelfth Group is Bryniau Dyfi.

Bryniau Dyfi 

North and then west of the Afon Dyfi (River Dovey) from SH 753 018 to SH 861 149, continuing south of the Afon Cerist to Bwlch Oerddrws at SH 802 170 and the Nant Tyn-twll to SH 767 167, continuing east of the Afon Clywedog to bwlch at SH 756 139 and the Nant yr Allt-oen and the Afon Fawnog and Afon Faw to Llyn Mwyngil (Tal y Llyn Lake) at SH 720 103, continuing east from stream at SH 724 102 to bwlch at SH 737 093 and following stream to SH 757 077 and the Afon Dulas to SH 753 018.  Bordering with the Aran to the north, Cadair Idris and Tarennydd to the west, Pumlumon to the south and Mynydd y Cemaes and Y Berwyn to the east.    

Twmpau - 200m updates

Mynydd Llwyn-gwern    276m    SH 766 045

This hill is promoted from the Sub-List as Harvey Maps have a 276m summit spot height, no spot height can be found on any Ordnance Survey map for the summit.  The bwlch has a 242m spot height on the Ordnance Survey enlarged Geograph map, giving this hill 34m of drop.

Sub-Twmpau - 100m updates

Cefn Llandybo    259m    SH 835 098

This hill has a 259m summit and 235m bwlch spot height on the Ordnance Survey 1:25,000 Explorer map as well as the enlarged Geograph map, giving this hill 24m of drop.

Pt. 247m    247m    SH 829 074

The Ordnance Survey enlarged Geograph map give this hill a summit spot height of 247m and a bwlch spot height of 226m, giving this hill 21m of drop.

Pt. 259m    259m    SH 789 047

This hill follows the Pt. notation as the blog author does not know an appropriate name for it.  It has a 259m summit spot height on the Ordnance Survey 1:25,000 Explorer map as well as the enlarged Geograph map, whilst the latter map gives a spot height on the area of the bwlch of 239m, giving this hill 20m of drop.

Next update due on the 7^th July 2014