Guest In Depth

Damming the floods

 

A proper system of community preparation and warning leading up to a flood event is as important as preventing a disaster.

Water management is a difficult undertaking. Among the most fundamental of human efforts of civilisation is ensuring enough water for our personal, agricultural, commercial, and industrial needs. Growing economies, populations and countries must continually adjust and make progress on their goals for adequate fresh water supply and the protection of life and property. Planners and decision-makers must account for an uncertain future without illusions or biases to cloud their judgment. In India, the monsoon brings life and death annually and scientists still puzzle over the anticipated effects of climate change and its impacts on weather, glaciers, floods, and overall water availability. As illustrated in India’s media following recent floods in Uttarakhand, sometimes water management goals are incompatible and are approached at crossed purposes. It should be recognised that those managing the execution of those plans, from community programs to massive infrastructure works, do only their best with the tools placed at their disposal when emergencies arise.

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Most dams in India, especially along the Himalaya front ranges, are built and managed for water storage and hydropower generation. In a country that sees tragic loss of life and productivity when the monsoon fails, that’s just smart planning. In the United States of America and Europe, we think we have these problems figured out. I say ‘think’ because much of the infrastructure was built in an era when historical patterns seemed stable and climate stationarity was the prevalent assumption. Now there is a growing recognition that stationarity was just a simplifying statistical approximation, designed to make engineering solutions more tractable and to support the proposal of infrastructure projects for government funding. The assumption of stationarity no longer serves when events, both droughts and floods, stray more and more often from the ranges that we expect based only on the historical record.

The US has more than twenty federal agencies, 50 states, and innumerable private utilities engaged in some manner of water management, with efforts proceeding locally and regionally under vastly different climate, weather, water resources, and financial conditions. The US National Weather Service (NWS), while having very little power over infrastructure projects, engages in a tireless campaign to educate the public and other agencies on the circumstances and dangers of droughts, flash floods, and river flood events. The NWS monitors drought conditions, providing forecasts of continued dry periods and potential relief when weather patterns change. Extensive NWS operations combine weather, stream and river observing and forecasting methods in order to warn the public about local and regional events. A critical interface between the NWS and several other agencies provides the science and forecasting capabilities to support efforts at infrastructure solutions to address these extremes.

The key lies in the management of that information and of the resulting infrastructure for its specific purposes. Agencies in the US have built dams that were originally meant for flood control but, over time and with population growth and frequent droughts, are now used (and consequently optimised) for water storage and hydropower production. That shift in priorities generally means keeping the reservoir pool higher to maximise service and profit. Flood control, however, requires keeping a lower reservoir pool (if any at all) to maximise the protection of downstream areas. These are obviously competing interests, and since floods are rare while the desire to see a return on the infrastructure investment only grows, the return-generating activity is often prioritised. This “scope creep” in the overall project purpose renders those dams almost useless for flood control.

Dam and reservoir management on major rivers is generally good, albeit with competing interests at times. On smaller rivers and streams, or in areas that see flash floods more than perennial flows, maladaptive management often falls far behind our understanding of the events themselves, and competing priorities sometimes take over. These are places where science, forecasting, modeling, and management can work together to bring about excellent flood control and protection. The science, forecasting, and modeling work well together and can provide a wealth of accurate, useful information. Difficulties arise in the transition of that science to practice: whether managers want that information, whether they have the capability and authority to make use of it, and whether they have the willingness to accept responsibility for the outcomes of their decisions.

Of course, dams last for decades, even centuries. As mere tools, their purposes can be adapted to the society’s needs. With the anticipated impacts of climate change on many regions’ precipitation patterns, we may see widespread repurposing of existing dams and many new infrastructure projects to fill gaps where certain purposes, such as flood control, are left unaddressed. At the same time, monsoon prediction is getting better in a seasonal and statistical sense, and IMD is improving its quantitative precipitation forecasting capabilities. However, the weather radar network remains focused on coastal areas and only a few of the inland locations prone to flooding rain storms. Hydrometeorological modeling efforts, whether for rainfall, streams or rivers are practically non-existent. Large rivers may get some attention for flood forecasting, but community protection requires both organisation and education, and still those communities often resort to hard infrastructure projects for some basic level of defence. Building and maintenance of that protection requires still greater organisation, as well as funding from any number of sources.

Dams in the right locations can help, but only if managed in an integrated, scientific approach to flood mitigation. There are many ways that management can help mitigate the dangers of floods even without dams. Monitoring, modeling, forecasting, education, warning, and evacuation plans can all go a long way to protecting people and their property, even before a dam is built. And if a dam is built for added protection, none of those other activities should stop: that hard protection cannot ever take the place of monitoring and preparation. The proper management of a flood control dam can help prevent a tragedy, but a proper system of community preparation and warning leading up to a flood event is just as important in preventing disaster.

Photos: _YattaCat_

Matthew Garcia is a hydrologist and a doctoral student in forestry at the University of Wisconsin-Madison, USA.

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