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Floods of the Past, Design for the Future
Validation of GRADE using numerical studies of historical floods
Design standards for flood protection in deltas require magnitude estimates of extreme (millennial) floods. The Dutch Delta Programme considers a design discharge of 18,000 m3/s an appropriate upper value the Rhine River at the German-Dutch border. Absence of a sufficiently long observational record of river discharge introduces considerable uncertainty in estimates of magnitude-frequency relations, which can only partly be solved by using statistical methods. Numerous historic flood marks along the German Rhine and sedimentary data of the youngest 2000 years contain valuable information on past extreme floods. In this interdisciplinary project we combine sedimentary and written archives from the delta with state-of-the-art reconstructions and 2D modeling of past events to quantify magnitudes of large historic floods of the lower Rhine. The resulting method and computations allow evaluating the potential limits to design flood magnitudes and inundation cascades in the current situation in the Netherlands and adjacent Germany.