By Pushpendra Johari
The frequency and intensity of rainfall-induced floods have increased in recent years. It’s not the usual monsoon rainfall patterns anymore. The monsoon’s vagaries have raised alarming concerns on the flood risks in various cities, especially in areas with no flood history. While high flood risk areas such as Bihar and Assam continued to experience floods, cities like Mumbai and Chennai have been encountering floods almost every year.
In 2020, the vulnerability towards floods has been rising, with cities like Jaipur and Hyderabad encountering never-seen-before floods caused by short-duration intense rainfall. The trend of global rainfall of the last century reveals that while the number of rainy days is decreasing, intense rainfall events (100-150 mm) per day are increasing. Here the algorithms go beyond climate change. While nature has its share, we have a more prominent role to play here. There are more reasons for this untimed peril.
Analysis Of High And Moderate Intensity Rainfall In The Past 120 Years (Source: RMSI)
Increasing Urban Risk
According to the Census of 2011, nearly 31 percent of India’s population live in urban areas. Due to increasing and extreme urbanization, urban areas are expected to house around 40 percent of India’s population by 2030. Massive, isn’t it? Even today, we are witnessing unplanned urban development leading to the poor drainage system for stormwater. The drainage system’s condition has deteriorated due to clogging of drains because of ineffective garbage collection in certain areas.
Besides, developmental activities in the form of newly built infrastructure (such as flyovers, roads, and buildings), the encroachment of dried-up lakes, and reduction in the city water bodies, wetlands, and greener areas have been diverting the rainwater run-off. Wetlands reduce the severity of floods and water-logging by storing water. But such unplanned urbanized initiatives have also affected the wetlands leading to a reduction in storage capacity.
The water-logging in high-tech cities like Hyderabad is a recent example. Who would have thought that in just 24 hours, the city would be waterlogged due to high-intensity rains? Flash floods wreaked havoc in the city beyond expectation. The current drainage system is unable to withstand such intensities. Mumbai’s drainage network is also an apt example in this case.
Putting the Pieces Together
For effective flood-proofing, there is a dire need to integrate strategies for reducing disaster risks in developmental planning. So, what does this mean? Before developing any area for residential/industrial purposes, a detailed multi-hazard risk assessment study should be conducted to assess the risk and ensure the development is disaster risk proof.
In case of floods, this information helps understand the area vulnerability towards varied rainfall patterns, estimating the structural, social, and economic impact of hazards and risks associated with other hazards such as earthquake, tsunami, cyclone and surge flood, drought, landslide, fire, etc. Consequently, the planning framework is shaped in terms of drainage network capacity and slope, ground floor elevation above the road level, garbage collection points, proximity of buildings, setting flood defense barriers, etc.
Technology to Draw the Roadmap
Untimely rainfall-induced floods cause a substantial direct and indirect impact on the communities, infrastructure, and economy. The situation demands building flood resilience through innovative technological solutions in the form of flood forecasting and flood risk assessment.
An effective flood forecasting system will help understand the risks and create effective response mechanisms to prevent/reduce the impact on lives, buildings, and infrastructure. The hydrological and hydraulic studies should be increased along with defining the flood zones to develop the city masterplan, and industrial developmental plans and policies. An effective preparedness, response, and recovery plans can avert such risks and mitigate the social and economic effects.
About the Author
Pushpendra Johari is the Senior Vice President – Sustainability at RMSI. He heads the sustainability practice that focuses on managing risks to water resources and natural resources and building up the environment through consulting and assignments from the government and multilateral funding agencies. He has over 25 years of experience developing GIS-based Natural Hazard Risk Assessment models and incorporating it in Software platforms. Hence, applying the results for creating mitigation, preparedness, response, and recovery measures.
He has been instrumental in the conceptualization and development of innovative IP solutions for the insurance sector. He is a global expert in climate change, water risk assessment, food security, and disaster risk reduction.
RMSI is a leading global natural catastrophe risk management consultancy offering solutions for risks associated with natural and human-made hazards. With more than two decades of experience, its expertise lies in hydrology, hydraulics, probabilistic hydro-meteorological hazard modeling, and climate change impact assessment. RMSI has vast experience of working in varied geographies such as India, Bangladesh, Vietnam, Morocco, Yemen, Sana, Nigeria, Timor Leste, Romania, and Beirut. It can help states develop flood risk assessment and flood forecasting models and create emergency action plans for the flood-prone zones.
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