Compound flooding - hydrographs and adaptation measures

We investigate compound flooding from river discharge and extreme sea levels in Lübeck, Germany, focusing on two storm surge barriers along the Trave estuary. We use hydrodynamic modelling to test these barriers under different flooding scenarios, including individual and combined flooding events. We demonstrate that during smaller combined floods, both barriers can reduce flooding. However, during larger combined floods, flooding can strongly increase due to the implementation of a surge barrier, which can prevent the river from discharging into the estuary, depending on where the barrier is actually located. Our findings highlight the importance of considering all types of flooding when planning flood defenses in order to avoid unexpected additional flooding and ensure effective protection.