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Intervention – Measurestaken immediately before andduring a flood event: Improving measurement andforecasting quality

Certain things need to be improved to help us better understand flooding. These include the accuracy of meteorological forecasting, and the measurement of precipitation and the subsequent analysis of how the precipitation affects runoff and flood waters in rivers. Data quality from river gauge stations varies along rivers, and this often affects the ability to make predictions downstream that rely on upstream measurements. Many river gauges are destroyed during large flood events and then do not provide any records, while others are imprecise when flow or water stages approach extreme values. More effort is currently being, and should still be invested, in improving network coverage (precipitation and river gauges) to feed better models with more accurate and reliable data based on improved measurements (such as better calibration of the stage-flow relationship). Declare a state of emergency as early as possible If forecasts provide earlier warnings when acute flooding is about to occur, this can save property, possibly lives, and give more time to responders to prepare for the flood crest. This principle has been applied with great success by the authorities of the Prignitz district in Brandenburg (see page 34 of report). Valuable time can be gained if decisions are made early, once there are indications to justify declaring a state of emergency. Instead of waiting until a fixed threshold is reached (for example, a certain level of flooding) a state of emergency can be declared when such thresholds are anticipated with, for example, 95-percent certainty, based on forecasts from upstream. This may give responders an additional 24 hours or more to set up emergency structures, rather than waiting until the alarm threshold is actually reached.

PERC Reports