Abstract

Washover deposits formed by overwash are important deposits for evaluating the stratigraphy and evolution of coastal environments. Examination of preserved washover fans also provide a palaeotempestological record that can used to inform on past and recent coastal risk with a view to predicting future coastal risk. To evaluate coastal systems and accurately recognise past washover deposits, requires detailed knowledge of the internal structure of recent deposits including washover fans. We used very high frequency Ground Penetrating Radar and satellite imagery to examine the internal architecture of the 31 st December 2011 Cyclone Thane surge-generated washover deposit on the beach that blocked the Then Pennai River at Thazhamkuda, near Cuddalore in Tamil Nadu Province, southeastern India. Cyclone Thane overwash overtopped the beach and deposited sediments on the contemporary beach and behind the beach within the former channel of the blocked river. The modern washover fan thus contains sediments that are preserved subaqueously Manuscript File Click here to view linked References and subaerially. We demonstrate that the internal architecture of the fan at Thazhamkuda is largely controlled by the pre-existing topography, and erosional and depositional processes as the cyclone washed sediment inland. At the landward margin of the fan, terminal foreset bedding is preserved and this sedimentary structure remains one of the only features that can discriminate storm and over tsunami deposits.