Abstract In order to mitigate against environmental impact, to satisfy the design criteria and to ensure the long-term integrity of the construction, the Transmission Department of Wales Gas sought geotechnical advice on the routing and design of a major gas transmission system. This system was being built to reinforce the gas supplies to the industrial valleys of South Wales. The opportunity was taken to apply geomorphological mapping at an early stage in route planning so as to avoid abortive design work on alignments which might subsequently prove unsuitable or too costly to engineer (Fig. 1). Pipeline engineers welcomed the approach, which commenced by obtaining an understanding of the client’s objectives and industry design guidance. Working as part of the project team, engineering geomorphologists provided guidance from initial routing studies through detailed design to construction, which was completed without contractual conflict arising out of unforeseen ground conditions. Fig. 1. Application of geomorphology to the development of a pipeline project.

Abstract The upper Palaeozoic Orogenic Province of SW England is a part of a belt of Devonian and Carboniferous basins that extended from Devon and Cornwall through to Germany, some 800 km to the east. Their complex sequence of basin development and phases of deformation, described in this chapter cumulatively comprise the Variscan Orogeny in this region. Synchronously with the Devonian events within the Variscan Orogen, the mainly fluvial facies of the Old Red Sandstone filled basins in the Avalonian continent north of the Variscan front (Chapter 6). During the succeeding Carboniferous, basins within the continent were mainly extensional in origin, until a period in the late Carboniferous when many basement faults were inverted (Chapter 7) resulting in uplift of the basin fill, that initiated a new palaeogeography at the start of the Permian. The South Wales Basin represents a transitional zone between the mobile Variscan belt and the continent to the north. This transitional position is reflected in the Devonian by the interdigitationof the Old Red Sandstone facies and marine sediments at the northern margins of the Variscan basins (Chapter 6). Throughout the Dinantian and Namurian the succession within the South Wales basin had much in common with successions in basins within the continent to the north (Chapter 7). It was not until the Silesian that Variscan deformation affected basin development and caused its deformation (see this chapter).