Floods in Himachal Pradesh point to the need of environmental planning to identify high-risk areas and avoid development there
Photo: @dprhp / Twitter There is growing scientific evidence of erratic rainfall events in India due to global warming and climate change. The current flood situation in Himachal Pradesh, Kerala floods in 2018, Chennai floods in 2015, and Kedarnath floods in 2013 were all caused due to extreme rainfall events that previously occurred at a probability of once in a hundred years but are more frequent now.
While extreme rainfall events cannot be controlled or avoided, one way to reduce the disaster risk is by promoting development in low-risk areas and protecting certain areas for environmental sustainability.
Hedonic pricing research has shown that hoteliers and real estate developers tend to develop in areas like hill tops and along rivers and lakes due to aesthetic views they offer and the high economic returns. But they do so without understanding the risks or the violations of environmental legislations.
Hilly areas are prone to flash floods caused by cloudbursts and extreme rainfall events that also trigger landslides. Development in hilly and riverine areas require careful environmental and land use planning including hazard risk and vulnerability assessment to reduce disaster risk and for environmental sustainability.
The Maradu flats in Kochi (which were demolished) is an example of violation of the Coastal Regulation Zone rules. In Bengaluru, the National Green Tribunal came down heavily on construction in the buffer zones of lakes and riverbeds that violate buffer zone guidelines. In Himachal Pradesh too, there has been rampant expansion of tourist homes and other buildings. But it is the home buyers and naive investors that face the wrath of legislation and nature’s fury even when they are unaware of environmental violations.
Environmental planning helps in identifying low and high-risk areas by using Geographic Information System and satellite imageries.
Environmental planning involves spatial overlay of layers like land use, hydrology, soil, slope, hazard map, ecologically sensitive areas, etc. with weightages given to each layer. This helps to identify suitable and non-suitable land parcels for development.
For example, slopes above 25 degrees, rivers, probable flooding areas and forests are given high weightage and the resulting map shows land parcels suitable for development and those that are in need to be preserved for environmental sustainability.
The Himachal Pradesh Town and Country Planning Rules 2014 has set the maximum acceptable slope for development at 45 degrees. It bars construction along flood prone areas and the development should be away from Highest Flood Level (HFL).
But the HFL for various rivers and tributaries is not available especially under extreme rainfall situations.
Environmental planning, with hydrology models and Intensity Duration Frequency curves of rainfall, helps to estimate the surface runoff, stormwater and river flows and identify potential flood areas, including in cases of extreme rainfall events. Such areas can be marked as high-risk zones to avoid future development.
In the example below, slope, hydrology and land use are used to generate a land suitability and risk map. The red areas show high slope and flood prone areas that are to be preserved for environmental sustainability, while other suitable land parcels that can be developed are identified.
With the availability of open-source satellite imageries and increased computational efficiency like Google Earth Engine and Python, environmental planning can be carried out at large scale and to the size of a state.
This can help in understanding risks in large areas like river basins and downstream areas.
Once such areas are mapped by state level nodal agencies like the State Disaster Management Agency, the information can be disseminated to urban development agencies, district administrations, department of town and country planning, etc. They can then discourage human settlement and development in high-risk areas.
Sustainable development in the hills by balancing the economic growth needs and environmental sustainability is a challenge. For example, the Western Ghats Ecology Expert Panel Report of 2013 that recommended 64 per cent of Western Ghats to be declared as an ecologically sensitive area was opposed as it may affect economic growth.
But reminiscence of the disasters in the last decade and the impending future disaster risk shows short term economic gains are meagre when compared to economic losses caused due to unplanned growth.
Environmental and land use planning with support of strong environmental policies is a possible way forward.
Dhanapal is an independent consultant on climate change and environment
Views expressed are the author’s own and don’t necessarily reflect those of Down To Earth
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