Large wood transport as significant influence on flood risk in a mountain village

• Published in: Natural hazards (Dordrecht) Vol. 74; no. 2; pp. 967 - 987
• Main Authors: Ruiz-Villanueva, V., Bodoque, J. M., Díez-Herrero, A., Bladé, E.
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01-11-2014; Springer; Springer Nature B.V
• Subjects: Civil Engineering; Damage; Deposition; Earth and Environmental Science; Earth Sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Environmental Management; Environmental risk; Exact sciences and technology; Flood damage; Flood flow; Floods; Fluid mechanics; Geophysics/Geodesy; Geotechnical Engineering & Applied Earth Sciences; Hazards; Hydrogeology; Mathematical models; Mountains; Natural Hazards; Natural hazards: prediction, damages, etc; Original Paper; Risk assessment; Streams; Transport; Urban areas; Wood; Iberian Peninsula; Southern Europe; Europe; Spain; ANE, Spain; Large wood transport; Drift wood; Woody debris; Flood risk; rivers; risk assessment; floods; damage; models; mountains; maps; streams; inundations; hydrodynamics; bridges; transport; urban areas; debris; wood; infrastructures; uncertainties; flow
• ISSN: 0921-030X; 1573-0840
• DOI: 10.1007/s11069-014-1222-4

An important issue that is not considered in most flood risk assessments in mountain villages in Spain is the transport of solids associated with the flood flow, in this case, large wood transport. The transport and deposition of this wood in urban areas may be a potentially worse hazard than the flood flow itself. Despite its importance, large wood is a key ecological element in rivers, so removing it could be an unsuccessful approach. Therefore, efforts are needed in the better understanding of wood transport and deposition in streams. To analyse this process, scenario-based 2D hydrodynamic flood modelling was carried out. Since flood risk assessment has considerable intrinsic uncertainty, probabilistic thinking was complemented by
possibilistic
thinking, considering worst-case scenarios. This procedure obtained a probabilistic flood map for a 500-year return period. Then, a series of scenarios was built based on wood budget to simulate wood transport and deposition. Results allowed us to identify the main infrastructures sensitive to the passing of large wood and simulate the consequences of their blockage due to wood. The potential damage was estimated as well as the preliminary social vulnerability for all scenarios (with and without wood transport). This work shows that wood transport and deposition during flooding may increase potential damage at critical stream configurations (bridges) by up to 50 % and the number of potentially exposed people nearby these areas by up to 35 %.