Last week, a flood on the Teetsa River swept through villages in the Himalayan mountains of India, taking out bridges and homes. At least 40 people were killed, with more than a hundred people still missing. The root of the disaster appeared to be a natural one, as an avalanche sent ice and boulders tumbling into a large glacial lake, causing it to overflow as a wall of water that surged downstream. But, as with most disasters, it’s hard to call this one strictly “natural” because human-caused climate change has made this type of event—a “glacial lake outburst flood”—more likely.
As the massive wave swept downstream, it obliterated the Teetsa-3 dam, a 1200 megawatt hydropower dam that was only a decade old and cost 1.5 billion USD to construct. This sudden loss of major infrastructure underscores another risk that climate change is amplifying: the vulnerability of hydropower and other dams to damage or destruction from floods that will continue to grow in magnitude.
Beyond the loss of expensive infrastructure, this rising flood risk to dams can pose real danger to people living downstream, as was tragically demonstrated last month in Libya when more than 10,000 people were killed the flood unleashed by the collapse of two dams on the Wadi Derna during record-breaking precipitation. Note that these were not hydropower dams and the structures had not been maintained in the war-torn country.
These are not isolated incidents, as examples can be found around the world.
In 2017, California’s Oroville Dam, the tallest dam in North America, came close to failing—unleashing what would have been a disastrous flood for hundreds of thousands of people living downstream—due to record-breaking precipitation and runoff. Floods damaged hydropower dams and triggered downstream evacuations in Puerto Rico in 2017 and Colombia in 2018.
In May of 2020, between four and seven inches of rain drenched central Michigan over a two-day period, resulting in flooding that led to the collapse of two hydropower dams and the evacuation of more than 10,000 people downstream as downtown Midland, Michigan was inundated by nearly 10 feet of water.
While Oroville was a near miss and, due to warnings and evacuations, the Michigan floods were not deadly, a much greater catastrophe occurred in Laos in 2018, when heavy rains led to the collapse of a portion of a hydropower dam, releasing a flash flood with a volume half that of the Mississippi River. The flood rapidly inundated nearly 20 square miles, displacing 6,000 people and killing at least 36 people.
These recent events are happening at a time when only 4% of all current hydropower dams are located within areas with the greatest risk of flooding – but that proportion will grow dramatically due to climate change over the next thirty years. I recently led research showing that, by 2050, the proportion of hydropower dams in regions with the highest flood risk will increase five times, to 20% of dams, due to projected climate change driving increases in flood magnitudes across much of the world.
Further, the new dams being built today are disproportionately located in regions where flood risks will increase the most: only 2% of currently planned dams are located in regions that today are classified as having the highest flood risk. But by 2050, 40% of all planned dams will be in the regions with the highest risk. These numbers are based on the same set of planned dams; it’s the regions where they are located that are predicted to change over the next three decades. (See this interactive map to explore current and future flood risk for hydropower dams around the world.)
The current and rising risk of floods to hydropower, and other, underscores three main points.
First is the absolute necessity of minimizing climate change. Global flood losses (all river floods, not just dam-related) will increase quite a bit even if we successfully hit the most ambitious climate target (keeping warming below 1.5° C). With that level of warming, the number of people exposed to river flooding is projected to increase by 50–60% and flood damages are projected to increase by 160–240%. Warming of 2° C would result in a doubling of the people affected by floods and an increase in damages up to 520% compared to today. This is a surprisingly large increase in losses relative to warming of 1.5° C, underscoring that seemingly small differences in temperature can have major differences in disruption to people’s lives.
Second is the need to dramatically increase investment in adaptation to climate change. As noted above, flood risk will still rise considerably even if we hold warming to 1.5° C – meaning considerable adaptation will still be needed.
There are a number of steps we can take to reduce risks associated with dam failure, encompassing both engineering interventions and Nature-based Solutions. These include retrofitting spillways to safely pass larger floods, managing watersheds to reduce runoff, and integrating better monitoring and forecasting into dam operations. Countries can adapt to increasing flood risk by giving rivers more room to spread out, and avoiding new development in areas at risk of flooding.
However, the financial challenge is stark. The United Nations Environment Programme (UNEP) estimates that current investment in adaptation is only 5 – 10% of what is needed. Moreover, many countries aren’t even keeping up with the maintenance and rehabilitation needed for current levels of risk. For example, the American Society of Civil Engineers gives a letter grade of “D” to both dams and levees in the United States, noting that rehabilitating these structures to maintain their safety will require more than $100 billion in investment.
Removal of aging and obsolete dams is gaining increasing attention as a solution for improving safety – while simultaneously being one of the most dramatic ways to restore river ecosystems (see this earlier post). In the United States, this synergy underpins the collaborative efforts of the hydropower sector, river conservation organizations and Tribes to secure funding for upgrading some dams while removing others, resulting in $2.3 billion in the 2021 Bipartisan Infrastructure Bill for these actions.
Beyond climate mitigation and adaptation, the rising flood risk to dams underscores the need to change how we plan future infrastructure. Such planning needs to be based on comprehensive assessments of both current and future risks. In addition to rising flood risk, hydropower dams also face increasing risk from water scarcity that will result in reduced generation, generally during times of greatest demand for electricity, such as during heat waves that spike demand for air conditioning.
This needed evolution in planning has implications for project-level development, as future dams should be planned and designed for the hydrological conditions they are likely to experience, not those of even the recent past.
But even more importantly, the planning of infrastructure systems should fully consider a range of alternative solutions to these risks, such as land-use planning and reconnecting floodplains to reduce flood risk and diversifying generation technologies to reduce climate-driven risks to energy. For example, solar panels and wind turbines are generally not vulnerable to floods and solar panels operate near their peak capacity during hot, sunny drought periods when other generation sources are stressed (aside from hydropower dams, nuclear and thermal plants also can see generation curtailed during droughts due to depletion of cooling water sources).
The recent disasters in India and Nepal are warnings that climate change will drive considerable increased risk to people and energy infrastructure. But we have a range of solutions for reducing that risk while also restoring and protecting nature.
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