Integration of EM techniques for mapping buried historical harbours: a case study from the archaeological site of Tell el-Rub'a, Egypt

This study focuses on the integrated application of the frequency-domain (terrain conductivity, TC) and transient electromagnetic (TEM) methods to map an ancient riverine harbour (port) at the Egyptian archaeological site of Tell el-Rub'a (prehistoric Mendes). Fifty-one TC profiles were measured using six EM frequencies and sixteen TEM soundings were performed at the selected site. The apparent conductivity maps derived from the TC survey enabled defining the lateral extension of the harbour basin and its edges to penetration depths ranging between 12–30 m. The vertical extension of the harbour basin was determined using the TEM inversion. Three layers were defined: the topsoil, the conductive silty clay infill, and the resistive sand bedrock. The bedrock is found at depths ranging from 19 to 31 m. The TC and TEM results were combined to form a 3D image of the harbour basin. This study confirms the existence of Mendes harbour and demonstrates the effectiveness of the TC and TEM methods for such archaeological studies.