Mapping Thickness of Raised Peat Bog Deposits Using GPR

The Irish Midlands have a unique landscape resulting from the retreat of the last ice age and subsequent post glacial deposition, forming extensive areas of raised peat bog. These natural resources have been used extensively for the supply of energy from domestic peat cutting to the generation of electricity on a large scale. In order to manage these vast areas there is a need for an accurate method to assess the remaining reserves and to aid future production planning. To achieve this a LIDAR survey was carried out to provide elevation data over the entire infrastructure, and accurate peat thickness data is required for approximately 35,000Ha of production bog. GPR was used to provide this thickness information and the accuracy of the data was confirmed by peat probing. The survey showed three distinct GPR signatures associated with the presence of the three main sub-peat soils, namely gravels, plastic clays and shell marls, as well as from internal peat layers. This paper describes the work carried out at Blackwater Bog, an area of 1,890Ha of raised bog east of the River Shannon in County Offaly and presents examples of the different GPR responses.