Lost water bodies and a flooded city – Counterfactual scenarios of the extreme Chennai flood highlight the potential of nature-based solutions: A Sneak Peek

Kunal Konar
May 20
2 min read

Author: Dr. Nithila Devi Nallasamy, Post-doctoral researcher at GFZ-Potsdam, Germany

Prologue

I am very elated to share our recent publication here titled, "Lost water bodies and a flooded city – Counterfactual scenarios of the extreme Chennai flood highlight the potential of nature-based solutions".

Our work focuses on analyzing the role of water bodies (locally called 'tanks/eris') in flood moderation of an extreme flood event. These water bodies are formed by damming the naturally occurring valleys in the Deccan Plateau of India. Since the early 1900s, urbanization has led to the loss of 13.6 million m3 of tank storage volume within the city. The remaining tanks, holding 174.7 million m3 of water outside the city, are now at risk.

The study uses the following two scenarios along with the existing baseline scenario (Figure-1):

Retrospective: The lost water bodies from the early 1900s within Chennai city had been protected during the urbanization;
Futuristic: The existing water bodies upstream of the city were also lost.

Results and Conclusions

The key info-graphic is shown in Figure 2. The following are the key takeaways,

Protecting water bodies that were lost within the city could have reduced damages by 17% and population at risk by 25.3%.
Existing water bodies, if lost, increase damages (44%) and population at risk (40.5%).

Figure-2: Comparison of a) With tanks and b) Without Tanks Scenarios w.r.t the Baseline Scenario

The End?

This paper is close to my heart, as it stems from the field visits, I undertook during my undergraduate studies to villages around Madurai in South India, where I witnessed the impact of disappearing water bodies on the livelihoods of the local community.

I sincerely thank all my co-authors, Abinesh G, Nivedita Sairam, PhD., Heiko Apel, Sergiy Vorogushyn, Heidi Kreibich, Andre Felipe Rocha Silva, Soumendra Nath Kuiry and Laurens Jozef Nicolaas Oostwegel for their valuable contributions in developing and shaping this manuscript.