Shoreline changes caused by erosion and accretion are natural processes that occur at various time scales. They can happen as a result of the longterm, and short-term events like storms, regular wave action, tides, and winds. Most coastlines are dynamic, and erosion cycles are frequently an important feature of their ecological character. Wind, waves, and currents are natural forces that easily move unconsolidated sand and soils in coastal areas, resulting in rapid changes in shoreline position, particularly in the monsoon season.
Traditionally, there are two options for combating coastal erosion: hard structural/engineering options and soft structural/engineering methods. These solutions have at least two hydraulic functions for controlling waves and transporting littoral sediment. Because they have weaknesses when used alone, a combination of hard and soft options has recently become more popular for optimum results.
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Beach nourishment is soft engineering method which is the mechanical/hydraulic placement of sand on the beach and/or shore to advance the shoreline or to maintain the volume of sand in the littoral. It is a soft protective and remedial measure that leaves a beach in a more natural state and preserves its recreational value. Sand nourishment can be done at various points along the shoreline or in the profile. Shoreface (underwater nourishment or profile nourishment), dune zone (landward and seaward above dune toe), beach, and swash zone are the nourishment options in cross-shore profile.
Sand dunes are an ideal coastal defence system, and the vegetation on them is critical for dunes’ survival because their root systems bind sediment and facilitate dune sediment buildup. During a storm, waves can reach the dune front and draw sand onto the beach, forming a storm beach profile; during the rest of the year, the wind blows the sand back to the dunes. Sand fences and mesh matting, in conjunction with vegetation planting, have successfully regenerated dunes through sediment entrapment and vegetation colonisation during dune construction or reconstruction. Coastal revegetation improves beach slope stability, consolidates sediment, and reduces wave energy moving onshore, protecting the shoreline from erosion, according to studies and scientific results.
Geosystems have been deployed globally for hard structural engineering solutions. Breakwaters made of sandbags, geotubes, and other materials have been successfully tested and found to be effective in halting beach erosion.
Artificial oyster reefs have been used to restore eroding coastlines by mimicking the effect of natural coral reefs. By dissipating wave energy, these massive natural submerged breakwaters protect beaches from storms and erosion. As per a report a substantial amount of sand was deposited landward of this artificial reef. As a portable and quick deployable method, flexible plates or membranes that float and act as wave breakers in a beach zone are also preferred. Any of these measures can be easily adopted for beach erosion in Goa.
