As the climate is changing, the risk of disastrous floods continuously rises. To minimise the subsequent increasing harms for citizens and their assets the implementation of flood protection systems is essential. To avoid defeats of such important and complex projects, this article researches potential reasons of delay and failures of past projects. Therefore, we complemented an expert interview with a document analysis to identify factors that are critical to the successful implementation of such systems. Using this methodology ensures grounding for the practical relevance and explicate lessons learned from past project. The extracted knowledge can be used to avoid future conflicts and failures. The findings concentrate on 4 factors – a proper planning, finding external experts, demand for protection and ensuring funding – that are fundamentally important to complete these projects successfully.