Sea Erosion Impacts Colombo
Colombo shoreline’s erosion percentage which was between 20-25 per cent in 2000 had increased to a gross 67.93 per cent by 2019, impacting Colombo District’s 24.3 kilometre long coastline, an Asian Development Bank Institute (ADBI) study uploaded on the ADB website on Thursday, on coastal erosion in the Western Province and coastal accretion in the Wayamba, warned.
Studies showed that the Colombo District, over a 15 year period beginning from 2005 and ending on 2019, was losing its shoreline at the rate of 0.54 metres per year on average in the review period, ADBI said.
The study further revealed that the erosion rate in the Colombo District has increased when compared with the erosion rate before the year 2000. By 2000, Colombo’s erosion rate was only between 0.0 and 0.1m per annum, the study said.
Colombo City in particular, with mass development projects, will increase the coastal erosion of their particular area, the ADBI report warned. Coastal erosion directly and indirectly creates environmental issues, reduces economic growth and generates social conflicts, ADBI further warned.
Monitoring of coastal zones is a significant task in sustainable development and environmental protection due to their (coastal zones’) highly dynamic nature, the study said.
In Sri Lanka, several major economic activities take place on the ‘coastal zone,’ like tourism, fisheries, fishery harbours, commercial harbours, development projects such as power generation schemes, the location of approximately 70 per cent of tourist hotels and nearly 62 per cent of industrial units, ADBI said.
Meanwhile, the increasing coastal erosion rate in Colombo may have been caused due to the destruction of natural barriers like corals and protective vegetation like mangroves due to the vast destructive phenomenon of the tsunami and, over time, different development projects that have carried out physical alteration of the shoreline within the past 15 years, ADBI said.
To conserve the coastal zone, Coastal Conservation & Coastal Resource Management Department (CC&CRMD) built hard protective structures with the collaboration of reputable organisations. However, these structures provided only a temporary solution to coastal erosion by preventing the degradation of the beach, ADBI said.
As the majority of them are revetments and breakwaters of the Colombo Port City (CPC) Project and Colombo’s commercial harbour, they may cause an increasing erosion rate in the other two districts in the Western Province, namely Kalutara to the South and Gampaha (Negombo area) to the North due to the effect of long-shore sediment transportation and seasonal winds, ADBI warned.
Furthermore, the application of hard structures has negatively affected the coastal scenery and many beaches with high tourism potential now have little scenic value, ADBI said. The negative visual impacts include the result of environmental degradation associated with the construction of hard protection structures and the collection of coastal debris, it added.
CPC combined with the Colombo South Harbour Project was the major development activity causing physical alterations of the shoreline in Colombo. Within the past few years, it may have caused the highest erosion and accretion rates around CPC.
In 2005, the greatest application of hard structures to prevent sea erosion took place within the Colombo District. However, the CPC development project caused this application to decrease from 2014 to 2019 because of the removal of hard structures around the region that covered the CPC and the damage to the revetments in certain places consequent to CPC development works.
The mass artificial landfilling CPC development project begun in 2014 has now expanded over 269 hectares as an additional part of Sri Lanka in the Colombo District. Howbeit, landfills are a major issue in shoreline management planning which aims to manage the risks associated with flooding and coastal erosion, ADBI said.
If highly adverse activities occur around the coastal zone, they cause adverse behaviours of the sea and the aggravated behaviours of the sea tend to increase the human influence on the coastal zone. Therefore, it is important to study the dynamic nature of the shoreline with respect to wind patterns, current patterns, sea level rises and aid the development of natural barriers to help protect the coastal zone, ADBI in conclusion advised.
Anthropogenic activities are the leading factor in coastal erosion rather than natural scenarios such as a sea level rise, climatic changes, and natural disaster conditions, ADBI warned.
The application of hard structures is the solution that is least able to control coastal erosion in a large area because applying hard structure is good for the site but not very helpful for other adjacent areas. Therefore, as long as humans introduce no alterations, the environment will remain under its natural conditions.
‘If the shoreline is changing naturally, as humans, we have to adjust rather than alter it,’ the ADBI study said.
Furthermore, proper identification of the dynamic nature of the shoreline that is occurring due to the behaviour of wave patterns and coastal currents, obligatory subsidies for the conservation and management of the coastal zone, buffering capacity from natural coastal ecosystems and coastal-based industries are very important, it added.