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A new approach to classify urban coastal areas

  • Image: Mgiganteus [Public domain], from Wikimedia Commons.

IIT Bombay study proposal to account for ecological sensitivity to help developmental and planning authorities.

The recent homecoming of the olive ridley turtles highlighted how Indian coasts are hotspots to migratory animals. The vast 7500 km coastline of India, home to a variety of flora and fauna, is also inhabited by nearly 40% of the country’s total population. Developmental activities along the coastline are damaging the coastal ecosystems. Prof. Pradip Kalbar, Prof. Arun Inamdar and Mr Ravindra Dhiman from Indian Institute of Technology Bombay have developed a new objective method to classify urban coastal regions with the aim to overcome the shortcomings of the existing Coastal Regulation Zone notification by the Government of India. 

The current CRZ framework does not consider variations in the biodiversity or landscapes in different regions along the coast. The researchers emphasise the need to prioritise these factors when making decisions related to coastal regions so that they can be well planned and sustainable. The new method considers these factors and also gives a strong basis to argue in the court of law against the concession and relaxation requests made with vested interests, that could damage the ecosystem. 

The Government of India issued the Coastal Regulation Zone (CRZ) notification to regulate developmental and industrial activities along the coastline. Introduced first in 1991 and revised in 2011, the framework lays out regulatory procedures for activities to be carried out in different parts of the coastal areas. Although the primary objectives of the notification are the protection of livelihoods of traditional fisheries and conservation of the biodiversity and natural coastal ecosystem, the subsequent amendments made to give concessions and relaxations to developers, have diluted the original objective and compromised the protection of eco-sensitive zones.

Coastlines comprise seas, bays, estuaries, creeks, rivers and backwaters. The CRZ (2011) classifies coastlines all over India into four zones---CRZ 1 (ecologically sensitive areas like mangroves and coral reefs), CRZ 2 (specific economically important areas and areas that have already been developed upto close to the shoreline), CRZ 3 (open areas that are relatively undisturbed, excluding areas of CRZ 1 and CRZ 2) and CRZ 4 (territorial waters from low tide line to 12 nautical miles into the sea and areas pertaining to Andaman & Nicobar Islands, Lakshadweep and other small islands). The current classification, although a welcome move, does not offer any logic for the extent of protected zone and hence is not transparent and the interpretations are subjective because of unclear guidelines.

For example, CRZ1 says that development is restricted upto 500 m from the high tide area on the landward side. In CRZ 3, no development is permitted between 0-200 m from high tide line.

“There is no apparent scientific basis for choosing the distance of 500 m or 200 m in different cases. There are places where the restricted zone should cover more land to conserve the local ecosystem effectively. Also, there are areas within the 500 m distance where there is no ecosystem of significance that needs to be conserved”, remarks Prof. Arun Inamdar.

Unfortunately, the new CRZ (2018) also has similar shortcomings.

“It lacks any scientific logic and is likely to meet the same fate as earlier changes as it has not set any clear target on the environmental or ecological conservation front”, says Prof. Inamdar.

The researchers suggest a new classification method based on Geographical Information Systems (GIS) and mathematical models. GIS is a computer-based tool designed to capture and analyse all types of geographical data. Although this system helps in identifying the right features of land for future use, it does not incorporate regulatory decisions and preferences of planners. To address this shortcoming, the researchers used a mathematical technique, called the MCDM (Multi Criteria Decision Making), which evaluates a set of conflicting criteria in decision making, along with GIS.

“The method we have proposed has a strong scientific basis and the area classification is possible without human intervention. Hence, it is more objective and transparent”, explains Prof. Kalbar.

Though scientists have previously used the combination of GIS and decision-making models for applications like urban planning and food security, this study is the first to use it in classifying coastal regions.

The researchers used remote sensing data from satellites, existing literature on Mumbai’s coastal areas and other data from government agencies to estimate the land use and land cover. They then calculated the ‘Coastal Area Index’ (CAI) for each category based on the data, inputs regarding ecological sensitivity and decision-making models that included regulatory and planning decisions. CAI can range between 0-10 with higher number indicating more ecologically sensitive areas.

The new classification system also classifies coastal areas into four types---Class 1 (extremely sensitive areas below the water during high tides and are not assigned a CAI value), Class 2 (highly sensitive areas with a CAI value from 6-10, where developmental activities are prohibited), Class 3 (moderately sensitive areas with CAI values 3-6, where developmental activities could be permitted after comprehensive environmental impact assessment) and Class 4 (low sensitive areas with CAI values between 0-3 where developmental activities allowed after verifying other regulations). For example, the Thane creek, an ecological hotspot, is classified as 'highly sensitive'. Many parts of southern and western Mumbai, few kilometres away from the seashore have nothing left worth conserving and are classified as 'low sensitive'.

The advantage in using CAI is that it can be derived using open source satellite imagery resources and can be available to any agency/municipal body. Additionally, CAI classifies area at 30 m resolution for different coastal features, which is far more accurate than the current method of classification.

The study provides a framework for sustainable coastal area management by being objective, transparent and scientific.

“This system is based on decision science where criteria rely on the physical utility of coastal features rather than the subjective interest of stakeholders”, adds Prof. Inamdar.

Perhaps, we can now hope for well-planned cities along the Indian coasts that let us enjoy the sea views and also take care of the enormous biodiversity.