BOIFIMU - Driftwood and Flooding in Urban Environments (2016)

Summary:

Dead wood transported by waterways exacerbates the consequences of rises in water levels in urban environments, where it accumulates near structures and increases the risk of flooding. Two phenomena are increasing the number and scale of urban floods caused (or exacerbated) by the presence of driftwood: 1) first, the gradual spread of vegetation along riverbanks and river basins upstream of towns and cities over the past 60 years has increased the quantity of dead wood available, particularly for high rises in water levels liable to sweep a large quantity of wood in the direction of urban areas and (2) due to climate change, we expect to see an increase in the number and intensity of these water level rises in future decades (e.g. Hirabayashi et al., 2013).
The challenge of managing dead wood upstream and in urban areas is therefore a relatively new issue in our waterways and wood is not yet systematically taken into account as a risk factor in the absence of a rigorous assessment of the risks connected to wood, despite the fact that this risk is increasing (Le Lay, 2007) and that recent events have damaged urban crossings in Switzerland and Italy. It is therefore becoming vital to better understand the factors governing flows of wood transported by waterways and the consequences of these flows in particularly developed areas, i.e. urban areas.
This project aims to characterise the risk represented by wood in waterways passing through towns and cities, and identify current practices for assessing this risk and taking it into consideration, in order to provide managers with suitable common guidelines to reduce the risk of flooding in urban environments.