You know floods have caught the public eye when Bollywood makes a movie about it. The visuals of Abhishek Kapoor-directed Kedarnath captured the horrors of the 2013 Uttarakhand floods, but were not enough to propel administrative action that would stave off other floods that inundated urban and rural parts of India.
While cities like Mumbai, Kolkata and states like Bihar, Assam always saw flooding in the rainy season, floods seem to be the new challenge for states like Tamil Nadu, Andhra Pradesh, Kerala and even Maharashtra (remember Kolhapur floods). It’s clear now that such climate change-induced uncertain and violent weather is here to stay. What should become clearer still is that administrators and policymakers will have to be a few steps ahead of an impending flood.
Other than heavy rains, floods occur for a number of reasons: inadequate carrying capacities of rivers due to silting of riverbeds — humans are a big contributing factor — degradation of catchment areas of reservoirs, poor natural drainage in flood-prone areas, glacial lake outburst, cloudburst, sudden reservoir releases due to heavy rains in its catchment areas, etc. Other than the tragic loss of lives, floods cause an enormous drain on the economy as well.
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India’s situation is precarious
The report by the UN-backed Intergovernmental Panel on Climate Change (IPCC), in its India section, has warned the country of floods and droughts, among other environmental calamities, and urged policymakers to rectify past mistakes such as neglecting flood alert systems and ignoring hydrology while planning towns and cities.
The State of the Climate in Asia, a report by the World Meteorological Organisation (WMO), says that in 2020 alone, India suffered losses to the tune of $26.3 billion (Rs 20,000+ crore) due to floods. It’s a staggering number that can be lowered if we just plan, co-ordinate and act fast.
A quick reversal of climate change is unlikely and hence, we need to devise ways of living with floods — pretty much the same way we are living with the Covid-19 pandemic — and get back to normalcy as soon as the waters recede.
Flood management measures are categorised as Prevention (structural measures to divert or retain flood water), Protection (structural measures to avoid or limit flooding in vulnerable areas) and Preparedness (non-structural measures, such as forecasting to provide early warning and sufficient lead time for saving lives and reducing damage).
Traditional efforts at flood management have focused on structural systems, such as building embankments and other flood protection measures. And yet, the threat of floods is as high as ever.
Various government-constituted committees have made several recommendations focussed on developing a combination of structural and non-structural measures to manage floods.
However, it is clear that we are yet to take advantage of the advances made in water resources management, information technology, communication and instrumentation. One of the most important non-structural measures is providing flood warnings to government agencies and the population in flood-prone areas, much in advance so that the rescue and relief operations can be taken up with sufficient time in hand.
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A new approach is needed
In India, heavy rain warnings are issued by the India Meteorological Department (IMD), whereas flood warnings for all major rivers are issued by the Central Water Commission (CWC) and state water resources departments/agencies for select rivers in those states.
The conventional method for flood forecasting used by the CWC is based on gauge-to-gauge correlation between observed water levels at the forecasting station and the base station, which has been developed using historical water levels observed at these stations. The gauge-to-gauge system is capable of forecasting water level at a designated downstream site, but this approach has a limitation because it involves waiting until the water level is observed at the base station located upstream of the forecasting station. In the process, possible lead time to issue a flood warning is lost. Another major limitation is that the forecast is limited to select sites and not all along the river.
These limitations can be taken care of by adopting a hydrological modelling approach. In this method, the observed rainfall is converted into river flow at the base station before it is observed. It also predicts the water surface profile along the river so that the water level in the entire river reach can be monitored.
The improvement of lead time by three days or more is achieved using weather forecasts of rainfall and temperature issued by the IMD and other international meteorological agencies. The rainfall forecast data is used by the hydrological models to predict water levels in rivers 3-5 days in advance.
We need a forecasting system which gives answers to ‘where’ (in the river stretch), ‘when’ (at what time) the floods are likely to occur and ‘what’ is the likely increase in water level in rivers. This can be achieved by a real-time decision support system called ‘Flood Forecasting and Early warning System. The FFEWS hosts the hydro-meteorological data, weather forecast data, hydrological models and warning dissemination system. The warnings are automatically generated if water levels in rivers rise above the ‘Warning’ or ‘Danger’ level, and are disseminated through SMS, WhatsApp, e-mails, etc. with sufficient lead time to government agencies and the affected population.
Another important tool in the FFEWS is the real-time data acquisition systems, which records and transmits hydro-meteorological data, which is applied to simulate water levels generated by mathematical models.
We have already seen the successful implementation of such technologies by the CWC in major basins, by the Bhakra Beas Management Board in Satluj and Beas basins, and by the Water Resources Department of Maharashtra and Bihar in Krishna-Bhima, Kosi and Bagmati basins.
Until we find the answers to climate change that can ease flooding, or stumble upon Noah’s Ark, a country-wide implementation of state-of-the-art flood forecasting systems is the only way to go.
Dhananjay Pandit is the Director, Water Resources Management, at the Research Triangle Institute International, India. Views are personal.
(Edited by Prashant)