Flood warnings have improved, but struggle to keep pace with a climate-wrecked environment
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Flood warning systems are a cost-efficient way to prevent floods from destroying lives and livelihoods. While warnings don’t prevent flooding, they give advance notice of an impending flood to allow communities to prepare: bringing in extra emergency personnel, establishing temporary flood defences, securing clean drinking water, moving valuables or — for the most extreme events — evacuating. Getting the jump on an incoming flood also allows for the mobilisation of resources to accelerate the clean-up after a flood, reaching people in need sooner and reducing the impact.
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Flood warnings are one part of a larger flood forecasting system. Warnings are used to communicate the flood forecast to individuals, businesses and emergency responders. The best flood warnings don’t just provide information on the river level (which is often meaningless to users), they combine this information with an explanation of the potential impacts. For example: “River levels will rise rapidly causing widespread flooding. Damage to roads and property is expected.”
A flood forecasting system only becomes useful when the flood warning leads to effective action. The aim of flood forecasting systems is to provide as much lead time as possible. The difficulty is that the longer the lead time, the more uncertain the forecast can be.
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Increasingly, the effectiveness of flood forecasting systems is constrained by poor communication rather than forecast skill. Scientists were shocked that more than 200 people died in the western European floods of 2021. While the forecasts for this event were considered “quite good”, when surveyed, 35% of people in one of the affected regions in Germany said they had not been warned. In other cases, the flood warnings were received but they did not convey the severity of the impending event.
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