The Use of Ground-Penetrating Radar for Mapping Peatland Subsurface in Afforested Peatland Restoration

Peatland afforestation and drainage are major causes of upland peatland degradation and have resulted in ongoing issues including increased flood risk, biodiversity loss, and carbon emissions. The last decades have witnessed increasing global investments in peatland restoration, as exemplified in South Wales. Here, the peatlands of Pen y Cymoedd coexist as the UK’s highest altitude windfarm and are being restored post tree-felling through a process known as ‘forest-to-bog’ restoration. Yet, there is a definite need to improve understanding of the impacts and effectiveness of these interventions, which can be gained through the mapping and representation of peatland structure and in particular, its ecohydrological properties.

Traditional peatland investigations involving manual probing and coring are environmentally intrusive and time and labour intensive. However, recent studies have demonstrated that geophysical approaches such as ground penetrating radar offer an alternative approach, enabling peat depth to be rapidly surveyed over large areas. Afforested peatlands, however, present new challenges for both radar and probe-based approaches, for example, the presence of tree roots can obstruct the probe from reaching the true depth of the peat body and create complex reflectors on the radargram. There remains little guidance on appropriate use of ground-penetrating radar methodologies in afforested peatland settings, particularly on peatlands that have different hydrogeophysical properties resulting from various land use interventions.

In this study, ground-penetrating radar surveys were conducted on peatland sites representing four different condition states: intact, afforested, felled, and restored. The surveys aim to map peat depth and explore the structure of the shallow subsurface. We adjust the parameterisation and processing flows involved in ground-penetrating radar surveys to determine the most appropriate approach dependant on peatland condition and the purpose of survey. Furthermore, by comparing reflection properties from different peatland sites which were selected to replicate the successive stages of forest-to-bog restoration, the structural changes caused by forestry and subsequent restoration attempts are revealed. This research will therefore help to inform operational best-practice and policy of peatland restoration, both within and beyond Wales.