Extreme flood events at large central European rivers since the mid-1990s have led to severe economic, social, and ecological damages. Thereby the urgency of an improved societal management of flood risks became obvious. On the one hand, the question arises how the complex interrelations between extreme floods and their damages can be assessed more precisely. On the other hand, higher effectiveness of mitigation measures and preparedness play a major role. In addition, especially the medium-term changes caused by climate change and other global change phenomena need to be taken into account.

The integrated research project VERIS-Elbe analyses changes of risks caused by extreme floods in large river catchments and potentials for their integrated management.

The transnational basin of the Elbe River serves as a case study with a detailed investigation of the German part of the Elbe River flood plain. On the macro scale, the flood hazard, flood vulnerability, and damage generation are simulated with a high spatio-temporal resolution. Hereby, especially the medium-term climate and land use changes in the flood plain are considered at least until the middle of the 21st century. Based on this, mitigation alternatives in the areas of water management, river training, and spatial planning are conceived and analysed regarding their effectiveness and efficiency. Scenarios of the system dynamics and mitigation alternatives are compared and ranked with respect to flood risks and efforts for mitigation using new multicriteria assessment of methods.

• How may risks of extreme floods be holistically simulated with a high spatio-temporal resolution on the scale of large river basins? (Methodology)
• How do flood risks, flood vulnerability, and damage expectancy values alter through changing natural and societal conditions as well as through strategic alternatives of mitigation measures? (Cause-effect analyses)
• Which socio-economic and ecological effectiveness and comparable cost-efficiency do the strategic alternatives of mitigation measures show and which instruments can support their implementation? (Evaluation, implementation instruments)

Because of the complex research topic the scientific approach of VERIS-Elbe is determined by two dimensions of integration: On the one hand, disciplinary models are coupled in a model system of the flood risk system.
On the other hand, results of the model simulations are put in a planning context that ranges from the ex-post analysis over the formulation of scenarios including development trends and mitigation options to their ex-ante analysis, multcriteria assessment, and implementation.

Explanations: LISFLOOD: Rainfall-Runoff Model SMS: Surface Water Modelling System (2D-hydrodynamic-numerical modelling system for surface waters) WAVOS: Water Level Prediction System (Wasserstandvorhersagesystem) HOWAD: Flood Damage Simulation Model (Hochwasserschadens-Simulationsmodell) DTM: Digital Terrain Model

The project consists of six subtasks with specific work packages:

1. Integration, coordination, communication
Responsible: J. Schanze

2. Setup and coupling of the flood models
Responsible: G. H. Schmitz

3. Setup of the damage simulations model
Responsible: C. Deilmann

4. Multicriteria analyses of the retention potentials of the whole flood plain
Responsible: B. H. Horlacher

5. Design of scenarios of extreme floods
Responsible: J. Schanze

6. Ex-ante analyses and assessment of the scenarios
Responsible: J. Schanze

VERIS-Elbe aims at the provision of basic and applicable results referring process knowledge and simulation methods which allow a simulation of flood risks on the scale of large catchments with their spatial allocation and temporal dynamic. Furthermore, findings will allow to specify the effectiveness of mitigation more precisely. To ensure a maximum of societal benefits of the research outcomes, an intensive coordination with relevant decision makers such as the International Commission for the Elbe, the federal and federal states ministries of environment and spatial planning as well as larger cities will be realised.