Key infra in Mumbai, other coastal cities may submerge by 2050
The analysis by RMSI, a global risk management firm has found that Haji Ali dargah, Jawahar Lal Nehru Port Trust, Western Express Highway, Bandra-Worli Sea-link,and Queen’s Necklace on Marine drive, all in Mumbai , are at risk of submergence.
A new analysis on the impact of sea level rise on coastal Indian cities has revealed that some critical properties and road networks in Mumbai, Kochi, Mangalore, Chennai, Vishakhapatnam, and Thiruvananthapuram will be submerged by 2050.
The analysis by RMSI, a global risk management firm has found that Haji Ali dargah, Jawahar Lal Nehru Port Trust, Western Express Highway, Bandra-Worli Sea-link,and Queen’s Necklace on Marine drive, all in Mumbai , are at risk of submergence.
RMSI considered findings from the Intergovernmental Panel on Climate Change’s sixth assessment report ‘Climate Change 2021: The Physical Science Basis’ released in August last year; various publications based on the IPCC report , the latest climate change data, and its own models to find out possible impact on the Indian coastline.
Six coastal cities of India , Mumbai, Chennai, Kochi, Vizag, Mangalore, and Thiruvananthapuram were considered for this analysis. RMSI’s experts created a high-resolution Digital Terrain Model (topography) for the coastline of the identified cities. They then used a coastal flood model to map the cities’ inundation levels based on various sea-level rise forecasts.
IPCC has projected that the sea level around India will rise significantly by 2050. ‘Assessment of climate change over the Indian region’ a report of the Ministry of Earth Sciences (MoES) also said that sea-level rise in the North Indian Ocean (NIO) occurred at a rate of 1.06–1.75 mm per year during 1874–2004 and has accelerated to 3.3 mm per year in the last two and a half decades (1993–2017), which is comparable to the current rate of global mean sea-level rise.
The moderate emissions (RCP 4.5) scenario of IPCC projects that steric sea level (variation in the ocean volume due to density changes) of the north Indian Ocean will rise by approximately 300 mm (a foot) relative to the average values from 1986 to 2005, the MoES report said. The corresponding projection for the global mean rise is approximately 180 mm.
“While we talk about sea-level rise, that is not the only factor that can inundate coastal cities. At 1°C global change, coastal regions are already facing the brunt of climate change with increasing intense cyclones, storm surges, and heavy rainfall events that lead to coastal flooding. While cyclones on the west coast have increased by 52% over the last four decades, extreme rains causing floods have seen a threefold rise since the 1950s. By 2050, the global temperature change will be close to 2°C, and these cyclones and heavy rains are projected to intensify further, putting the coastal cities in danger,” said Roxy Mathew Koll, climate scientist, Indian Institute of Tropical Meteorology.
He added, “The accelerated sea-level rise can compound coastal flooding due to these events, raising the water level and resulting in floods that cover larger areas for longer times. We need to urgently monitor and study these compound events (where multiple extremes overlap) so that we can prepare our early warning systems for efficient disaster management.”
In Mumbai, around 998 buildings and 24km of road length will be affected by potential sea-level rise by 2050, and approximately 2,490 buildings and a road length of 126 km will be affected by potential sea-level rise during high tide, the analysis found. In Chennai, with the potential sea-level rise by 2050, road length of 5 km and 55 buildings are at the risk, of which the majority are residential buildings situated in low-lying areas.
In Kochi, around 464 buildings are likely to be impacted by 2050 with the number rising to around 1,502 buildings during high tide. In Thiruvananthapuram, due to sea level rise by 2050 and sea level rise with high tide, 349 and 387 buildings, respectively, are likely to be impacted. In Visakhapatnam, around 206 buildings and 9 km of road network are likely to be inundated due to potential coastline changes by 2050.
“How much water will go inland is a function of what kind of continental shelf we have. The impact of sea level rise will be different in different parts. No client asked us to do these modelling studies. Because the IPCC report suggested Indian coastal cities could be in danger, we felt we should quantify these findings. We intend to reach out to affected state governments and we will definitely share the findings with the World Bank and National Disaster Management Authority,” said Pushpendra Johari, senior VP , Sustainability, RMSI Pvt Ltd.
Johari added that with early knowledge of how coastal cities are going to be impacted, some interventions can be made , including land reclamation; increasing the height of roads and strengthening buildings against corrosion or relocating them.
“We considered RCP 4.5 which is an intermediate scenario. Sea level is expected to rose at least 2050 and then stabilise,” he said.
The amount of greenhouse gases like CO2 emitted by the world needs to peak by 2025 followed by a 43% reduction in the 10 years after in order to limit global warming to 1.5 degree C by the year 2100, the Intergovernmental Panel on Climate Change (IPCC) said on Monday, calling for immediate action with a warning that policies implemented till the end of 2020 will add more emissions and lead to a rise of 3.2 degree C by the end of the century.
