StucK - Ensuring the drainage of coastal, urban spaces, taking into account climate change | Umweltbundesamt

An improved, short-term and small-scale precipitation forecast combined with radar measurements and model simulations (COSMO-DE-EPS) allows the operation of an operational runoff prediction model for urban regions. Its results clarify the warning service Inland Flooding Hamburg and thereby increase scope for action / reaction times in the event of a flood.

The method developed in StucK produces combined precipitation forecasts. These are based on the 1st-2nd Prediction hour on radar data. From the 5th prediction lesson, COSMO-DE-EPS data will be used. In between (3rd-4th prediction lesson) a superimposition of radar and COSMODE EPS data takes place. The combined precipitation forecasts are generated as an ensemble of 20 runs and significantly improve the forecast, especially for heavy rain warnings. The following products are created for this purpose:

1. Continuous time series of 20 ensemble runs, forecast period 0-20 hours
2. Continuous forecast images of precipitation intensity in mm / h, forecast period 0-20 hours
3. Predicted rainfall of 20 ensemble runs as sums over different time periods: 0-2, 0-6, 0-12 and 0-24 hours.

One work package aimed to capture the current state of the ecosystems of urban rivers and their floodplains and to quantify the potential impact of changing water management on ecosystems. Ecosystem conditions and processes underlying ecosystem services should be quantified and made available for socio-economic analysis.

The work package aims to quantify the ecosystem services of water retention in flood situations, carbon sequestration and pollutant immobilization of smaller urban streams, their flood plains and flood plains in Hamburg under the current and future changing water management conditions. To this end, an initial evaluation of the work so far available on this topic as well as regional and national water use models (such as the INFORM of the BFG) will be used to quantify ecosystem services.

A damage potential analysis procedure has been developed. Thus, the evaluation of different scenarios with regard to potential damage avoidance becomes possible. In addition, the results are suitable for communication and sensitization of the population (in the case of a hundred-year flood (HQ100) in the model region Kollau, the damage potential is around € 1.6 million).

Based on the optimized precipitation forecasts, a suitable management concept has been developed for the fast reacting water system of Kollau, starting 24 hours before the flood. The flood retention basins are controlled in such a way that they themselves, in the form of dry pools, and the aquatic meadows are ecologically upgraded. Flood protection measures will create ecologically valuable spaces. In the Dove-Elbe model region, the future management concept is already in place six days before the flood event occurs, as there are longer flow times and correspondingly earlier reactivation in order to create the required retention volume. The control of the complex control structure is optimized for this purpose with the help of modeling and combined with tide and precipitation forecasts.

The calculated damage potential of an HQ100 in the Kollau model region amounts to around 1.6 million euros. A developed scenario "future land use and climate change" shows an extension of the flooded area, so that an increase in the damage potential is still to be expected here. With these figures, the costs of protection measures are being revalued, including the creation of ecologically valuable spaces.