A pilot study has identified hotspots in Himachal Pradesh that are likely to be most affected by cloudbursts and monsoon downpours; this can help reduce risk from such disasters
Even as heavy rains in the Himalayan state of Himachal Pradesh in the past few days has led to flash floods, loss of lives and widespread damage, a pilot study on flood risk due to climate change provides information on the potential monsoon flood magnitudes that can be expected, and warning times that are possible — two key factors for the design of risk reduction strategies.
An Indo-Swiss team of scientists integrated three components of flood risk — hazard, vulnerability and exposure — to assess flood risk in Himachal Pradesh, and discuss how the results can be fed into adaptation planning. They report that contrary to the popular belief that the greatest flood risk in the state is due to glacial lake outbursts, the greatest risk is due to seasonal monsoonal flooding.
The scientists conducted a state-wide assessment of glacial lake outbursts and the associated flood risk, which were used as proxy indicators for exposure and vulnerability. They next assessed flood risks due to seasonal monsoon rains and cloud burst-related deluges, and mapped the likely exposure along the main river valleys of Kullu district.
The integrated assessment of hazard, vulnerability and exposure helped them identify several hotspots of flood risk in Himachal Pradesh. In their report published in the September issue of Environment Science and Policy journal, the scientists say that over recent years, international climate science and policy are increasingly focusing on climate risk as an indicator of vulnerability to climate change. But there are few studies to demonstrate how climate risk can be assessed and integrated into adaptation planning at local, national and national scales.
Simon Allen, from the University of Geneva and one of the study authors, explained to indiaclimatedialogue.net that his team’s study is “the first study that has applied the full risk concept, emerging out of latest IPCC reports, to inform on-ground adaptation planning.”
Allen says that climate risk has, until now, largely been an academic concept. The study demonstrates that “by considering not only flood characteristics, but also the vulnerability of communities, and their exposure, for example, houses or roads that sit in a flood path, we can provide a much stronger basis for identifying hot-spots of flood risk where adaptation planning and response strategies should be focused.”
The study shows clearly that the threat of Glacial Lake Outburst Floods (GLOFs) exists across many districts of Himachal Pradesh. “Previous research in the area has focused on a handful of well-known, potentially dangerous lakes, for example, Gopang Garth Lake in the north, but we clearly show greater societal risk from GLOFs may be elsewhere,” Allen said.
The study also shows that “the greatest threat is not from glacier lakes, but rather from seasonal monsoon flooding that occurs every year, and that understanding of historical flood characteristics, using evidence from damaged vegetation (dendrochronology), can be used as a basis for a robust flood risk assessment.”
The scientists used the results from the study directly in the design of a combined monsoon flood and GLOF early warning system for Parvati Valley in Kullu district, one of the hotspots of risk identified in their study.
The results provided information on the potential monsoon flood magnitudes that can be expected, and warning times that are possible. Using these two crucial sets of information, the team prepared and submitted a detailed proposal for a warning system to national adaptation financing schemes.
The study has raised awareness at the community level through workshops, and with local authorities to help strengthen local capacities to deal with flood emergencies.
“Too often, adaptation planning is based on insufficient data and knowledge of past events, so for both GLOFs and monsoon flooding, we present a valuable step-forward in understanding of this threat in Himachal Pradesh,” Allen said. “Adaptation strategies need to be underpinned by robust science.”
This is particularly true for the Himalayan region where there are many data gaps. “Sadly, this knowledge generation step is often missing. The worst-case is that strategies such as early warning systems are installed in the wrong locations or are not adequate for the magnitude of the event expected.”
But mere data generation does not suffice, said Allen. The strategies and the underlying science need to be strongly supported by the local stakeholders and their support and trust takes time to build. “Short-cuts only lead to maladaptation or strategies that are not sustainable in the long term,” he told indiaclimatedialogue.net.
Scientists at the G B Pant National Institute of Himalayan Environment & Sustainable Development, Almora, in the neighbouring Himalayan state of Uttarakhand, say the new study has filled gaps in current knowledge of the impacts of warming over the Himalayas.
The radiative balance — the balance between the amount of energy received by the earth from the sun and the energy it emits back — has changed in the Himalayas in recent years due to human activities, said institute scientist Jagdish Chandra Kuniyal. This imbalance “directly or indirectly results in the common incidents of fast glacier melting, glacial lake outbursts floods, cloudbursts and flash floods,” he told indiaclimatedialogue.net.
The contributing human activities include mass tourism; developmental interventions such as roads and hydropower projects; and the practice of slash and burn type of farming in certain pockets of the Indian Himalayan region — all of which release aerosols, or tiny highly-polluting particles, including black carbon or soot.
Aerosol studies from April 2006 to March 20013 and later extended to 2017 indicated a large absorption of solar energy by black carbon over the Parbati glacier in 2015 and 2016. The average temperature rise in Kullu valley is about 0.9 degrees Celsius, considering 1965 as a base year, said Kuniyal.
With the help of similar studies, India’s National Green Tribunal (NGT) has intervened by limiting the number of vehicles plying in the Rohtang Pass (3978 m above sea level) area to 1,200 tourist vehicles to reduce the pollution load, Kuniyal said.
The institute has been witnessing the impacts of climate change on ground level as well. Apple cultivation has now shifted up to 2,000 m at Katrain in the Kullu valley, from 1,000 m at Bajaura in 1965. “Similarly, other vegetation too has been found to be shifting toward higher altitudes due to climate change,” said Kuniyal. “As an adaptation strategy, farmers have now started to grow vegetables in low-lying areas from where apples have disappeared.”
The new study by the Indo-Swiss team “has, no doubt, filled up some gaps in existing knowledge,” Kuniyal said. “But how these findings will be implemented is a challenge at the policy level.”