Erosion processes driven by monsoon events after a beach nourishment and breakwater construction at Uswetakeiyawa beach, Sri Lanka

Abstract

The first beach nourishment project in Sri Lanka was carried out in 2012 over a 1.8-km stretch in the Uswetakeiyawa area by the Coast Conservation Department. About 300,000 m 3 of offshore sand in the Indian Ocean was pumped using a dredging vessel for the nourishment. Three breakwaters were constructed nearly 1 year after the beach nourishment. This research was carried out to analyze the performance of the above soft and hard engineering coastal protection strategies. Beach profiles and grain size data were collected over a 1-year period. This monitoring program covered entire seasonal cycles with a comparison to the pre-nourishment beach profiles. Satellite images were also analyzed spanning much larger time periods from 2010 to 2015. Beach profile data indicated both sand accretion and erosion in the nourished area. However, the variations of sand deposition showed enhancement of the sand volume. Satellite images indicated the irregular changes of the beach profiles after the construction of breakwaters. The field observations and calculated relationships of the breakwaters demonstrated either subdued salient or gap erosion at the specific locations of the nourished beach. In this study, no permanent or periodic tombolo formations were observed at Uswetakeiyawa beach. The lack of sediment supply from longshore currents and the high-energy cross-shore monsoon currents can enhance coastal erosion related to the presence of the breakwater.

Distribution and cementation characteristics of beachrocks along southern, southwestern and western coast of Sri Lanka

“…Figure 5 illustrates a typical XRD spectrum of a Sri Lankan beachrock sample showing the presence of heavy minerals. Overall, most common heavy mineral present in the Sri Lankan beachrocks in the studied area is ilmenite along with few others including magnetite, spinel, rutile, zircon, monazite and garnet which is in good agreement with the details documented by previous researchers (Cooray 1968;Katupotha 2003;Ratnayake et al 2018).…”

Coastal landscape evolution in the Wilpattu National Park (NW Sri Lanka) linked to changes in sediment supply and rainfall across the Pleistocene–Holocene transition

“…Likewise, the upper surface of the shallow‐marine prograding sandstone body in the lower part of the Point Kudrimalai section (Beds 1 and 2) is situated 9.0 m AMSL. The revealed SW‐to‐NE palaeo‐current direction (Figure 3) is consistent with a net annual littoral drift towards the north at the present‐day, which is associated with the SW monsoon (Ratnayake et al, 2019; Figure 8a). As the western coast of Sri Lanka is on the lee side of the island during the NE monsoon, there is no longshore drift from the northeast that might affect the coastal morphology (Venkataraman, 2011).…”

Blue Economy and Blue Finance: Toward Sustainable Development and Ocean Governance

“…Recent studies have revealed that the erosion of the coastal zone of Sri Lanka is a long-standing problem (Lakmali et al 2017;Ratnayake et al 2018Ratnayake et al , 2019 but has poor monitoring and documentation. Other than that, studies on shoreline changes have been very limited in the Western and North Western provinces.…”