Urban flood real-time forecasting and modelling: a state-of-the-art review

Abstract

More than half of the world’s natural disasters are floods, affecting millions of people every year. In fact, more than 3 billion people have been affected by floods over the last century, i.e. half of the current world population! Urban floods have long been considered as unpredictable and unavoidable natural disasters. Continuously increasing urbanization has led to an increasing flood risk whereas technological growth has raised various new strategies to predict and face this risk. Most of the urban drainage networks are aging and have been designed to manage a maximum rainfall, or so-called design rainfall, which refers to a design return period (usually 10 to 100 years). Thus, this implies an “accepted” flood risk for a rainfall greater than the design rainfall. But this flood risk can be underestimated considering factors like city growth, flash floods and climate change. Thus, being able to forecast the flood is one of the main issues of integrated flood risk management. Various flood forecasting systems have been developed and used, a lot using a large range of advanced tools and some as part of integrated decision support systems. Runoff and hydraulic models are usually essential elements for such systems, as pre-studying tools or as components of the system. This paper intends to make a review of current urban flood forecasting systems as well as the available modelling technologies, focusing on urban drainage modelling. Different types of urban real time systems are assessed and evaluated to sort out the current state-of-the-art and to give recommendations for future urban flood forecasting systems.