Developing an operational forecast system as byproduct of scientific research - an example for inland floods at the German North Sea coast

Within the research project RUINS we assess the risk of inland floods of the Krummhörn region at the German North Sea coast. One third of this area lies below mean sea level, which demands to drain inland water during low tides by sluicing or otherwise by pumping. If, at any point in time, the drainage demand exceeds the drainage capacity, the available storage in polders and canals will be filled. Once this storage capacity is exceeded inland floods will occur.

Previous risk assessment for such inland floods assumed a constant daily drainage capacity, which results from the installed pump capacity. We analysed process data provided by the operator of the drainage system (1. Entwässerungsverband Emden) at sub hourly resolution. The recorded water levels within the canal system showed that under current conditions the maximum areal drainage capacity is usually limited by the flow capacity within the canal network. The capacity of the pumps is dependend on the gradient from canal to North Sea water level.

Under increased tidal water levels in the North Sea (e.g. storm flood situations) the pumping capacity can drop below the canal flow capacity. In consequence the areal drainage capacity is variable and can become much smaller than the constant daily drainage capacity assumed in previous studies. Due to the predicted increase in mean sea level with climate change the area might face an increased risk of inland floods despite a situation of insignificant changes in predicted rainfall patterns.

Instead of costly infrastructural improvements, we propose a forecast system i) to optimise the drainage capacity in foresight of short term extreme situations and ii) to enable preparation for inland floodings. The proposed system includes the inherent uncertainty of the analysed processes and predicts the magnitude of upcoming inland floods. Currently, we use synthetic data as drivers, but these shall be exchanged by available weather and tide level predictions. The forecast system is realized as online accessible app, providing an easy usable and understandable access point for the operator and the interested public.