Abstract
The Tsunami, which struck the east coast of India on 26th December 2004, caused huge damage to life, property and environment. Beyond the heavy toll on human lives, it had caused an enormous environmental impact. Kalpakkam located in the south east coast of India is one of the areas affected by the tsunami. At some locations along the coast around Kalpakkam, morphological changes, vegetation loss and fatality were reported. Later, a slew of remedial measures were initiated at Kalpakkam in 2006 and construction of coastal armoring in the form of Tsunami Protection Wall (TPW) of 3.2 km length was one of them. A study was undertaken to assess the impact of this TPW on the surroundings based on periodic measurements of High Water Line (HWL) before and after construction of the wall. Also beach profiles were made at selected locations to observe seasonal changes in sedimentation pattern (i.e. accretion and erosion). As the residential area at Kalpakkam is located between fishing hamlets at northern and southern side, it is necessary to understand the impact of TPW, if any, in the surrounding area and on the fishing hamlets. Towards this assessment, high resolution satellite data such as Quickbird and IKONOS were employed (for the years 2002, 2003, 2009 and 2011) to measure the HWL. In addition, monthly beach profiles were carried out to measure the sedimentation pattern at selected transects with the help of N3 Precision Level survey instrument for the year 2009. The detailed investigations and analysis revealed no significant impact on the beach morphology and sedimentation patterns due to the construction of TPW, within the residential areas as well as at fishing hamlets. The average variations in the position of HWL along the coast was 4.6m and sedimentation changes were in the range of ≈ 0.5m in the berm of backshore region and ≈ 1.7m in the swash zone of the foreshore region all along the study area. No adverse effect is observed and the variations observed are similar to that in an unarmored control beach. The study provides the confidence that multi-dated satellite monitoring together with the profiling of beach would suffice the need for understanding the changes in the beach morphology due to the construction of beach armoring.
Highlights
The shoreline changes and the beach morphology are of major concern for coastal communities as it has the potential to threaten their livelihood
Kalpakkam located in the south east coast of India is one of the areas affected by the tsunami Ilangovan et al (Ilangovan, Jayakumar, Gowthaman, Tirodkar, Ramana & Naik, 2005), Verma et al (Verma, Nair, Singh &Sasidhar, 2006), Kumar et al (Kumar, Naik, Ramanamurthy, Ilangovan, Gowthaman & Jena, 2008), Anandan and Sasidhar (Anandan & Sasidhar, 2008) leading to morphological changes, vegetation loss and loss of lives
A study was undertaken to assess the impact of the Tsunami Protection Wall (TPW) on the beach morphology at Kalpakkam and to the surroundings based on periodic measurements of the position of High Water Line (HWL) and sedimentation pattern i.e. accretion and erosion pattern
Summary
The shoreline changes and the beach morphology are of major concern for coastal communities as it has the potential to threaten their livelihood. Such protection walls run parallel to the beach and are built with concrete, wood, steel or boulders They are called bulkheads or revetments or seawalls and designed to halt shoreline erosion caused primarily by wave action and to protect coastal structures from various costal hazards. It was observed that the sea walls have both positive and negative impact on the beach morphology based on the design and location In this context, a study was undertaken to assess the impact of the TPW on the beach morphology at Kalpakkam and to the surroundings based on periodic measurements of the position of High Water Line (HWL) and sedimentation pattern i.e. accretion and erosion pattern. Raj et al (Raj et al, 2006)
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