Learning from the past to inform flood risk management: Analysis of public survey data in Belgium on flood early warning and response during the July 2021 flood

Abstract. In July 2021 an intense rainfall event resulted in severe flooding in Belgium as well as neighbouring countries. The Walloon Region of Belgium was severely affected with 39 fatalities reported; in the aftermath, the warning system was criticised. In this paper we assess the flood forecasting, warning and response system in the Walloon Region of Belgium for the July 2021 flood event. The analysis is based on an online survey of affected residents (n = 550) and investigates the reception of official warnings, the interpretation and trust in those warnings, and subsequent response behaviour. We find that among the respondents in the Walloon Region 33 % reported not having received any warning, and 56 % did not know how to respond effectively. We analyse the most important influencing factors across the warning chain using the Protective Action Decision Model as a theoretical framework and test influencing factors using logistic and linear regression models. We find that those who were most severely affected at the household level were less likely to receive an official warning. Additionally, flood experience, the level of perceived surprise at the household level, and perceived flood severity significantly influenced whether individuals knew how to respond to the upcoming flood. Despite the flood’s huge magnitude, those who took damage-reducing actions were more likely to report an actual reduction in flood damage. This analysis highlights the need to improve Belgium's flood warning system by ensuring timely issuance of clear warnings and underscores the benefits of enhanced flood risk awareness for damage reduction.