(Nant y Dderwen Deg) (Unclassified).
Grid Reference: ST 19897 77887. Parish: Cardiff, Glamorgan
When recorded: 1898-1908. Primary Source: OS 2nd Edition Maps. Secondary Source: GB1900 website

Allt Cae-dderwen (Unclassified).
Grid Reference: SN 74497 35147. Parish: Cilycwm, Carmarthenshire
When recorded: 1898-1908. Primary Source: OS 2nd Edition Maps. Secondary Source: GB1900 website

Allt derwen & park clyn (Field).
Grid Reference: SN 26891 24221. Parish: Llanwinio, Carmarthenshire
When recorded: Circa 1840. Primary Source: none. Secondary Source: Cynefin

Allt Tan-y Dderwen (Unclassified).
Grid Reference: SN 45264 55278. Parish: Llanarth, Cardiganshire
When recorded: 1898-1908. Primary Source: OS 2nd Edition Maps. Secondary Source: GB1900 website

Allt y Dderwen (Topographic feature).
Grid Reference: SN 46760 29625. Parish: Llanllawddog, Carmarthenshire
When recorded: 1898-1908. Primary Source: OS 2nd Edition Maps. Secondary Source: GB1900 website

Banc-y-dderwen (Unclassified).
Grid Reference: SN 62317 17889. Parish: Llandybie, Carmarthenshire
When recorded: 1898-1908. Primary Source: OS 2nd Edition Maps. Secondary Source: GB1900 website

Blaen-rhyd-derwen (Settlement).
Grid Reference: SN 38896 53468. Parish: Llandysiliogogo, Cardiganshire
When recorded: 1898-1908. Primary Source: OS 2nd Edition Maps. Secondary Source: GB1900 website

Blaenrhyderwen Lands (Field).
Grid Reference: SN 38975 53769. Parish: Llandysiliogogo, Cardiganshire
When recorded: Circa 1840. Primary Source: none. Secondary Source: Cynefin

Bod-derwen (Unclassified).
Grid Reference: SJ 24802 65486. Parish: Mold Rural, Flintshire
When recorded: 1898-1908. Primary Source: OS 2nd Edition Maps. Secondary Source: GB1900 website

Bron-Derwen (Settlement).
Grid Reference: SJ 07875 50435. Parish: Derwen, Denbighshire
When recorded: 1898-1908. Primary Source: OS 2nd Edition Maps. Secondary Source: GB1900 website