Using 'flood-excess volume' to assess and communicate flood-mitigation schemes

O Bokhove (1) , M Kelmanson (1) , T Kent (1) , Guillaume Piton (2) , J.-M Tacnet (2)

1 School of Mathematics [Leeds]
2 UR ETGR (ETNA) - Erosion torrentielle neige et avalanches

As interest mounts in natural water-retention measures and alternative flood-mitigation Nature-Based Solutions (NBS) as complementary options to civil-engineering measures, catchments and cities increasingly face a large number of possible protection strategies. We offer a straightforward and educational protocol, for quantified flood-mitigation assessment of protection strategies, targeted for effectiveness analysis and decision-making involving stakeholder participation. %jmtc{for effectiveness analysis and decision-making involving } It is based on the concept of flood-excess volume (FEV) i.e., volume exceeding a threshold and generating flood damage, and exemplified for recent extreme-flood events in the UK and France.The central question is: what fraction of FEV is reduced, and at what cost, by particular flood-mitigation measures? Quantification and interpretation of cost scenarios are facilitated using a novel visualisation of flood-alleviation basins as partially filled, 2m-deep square lakes with side-lengths of about 1-2km. We consider two 2015 floods of the River Calder in Mytholmroyd (Yorkshire, UK) and the River Brague in Biot (Alpes-Maritimes, France). Each case has different flood-mitigation measures: flow-attenuation features, tree planting and peat restoration, and reservoir storage (Calder), and; retention measures, flood-walls, and bed-widening (Brague). Our straightforward protocol enables fast exploration of protection strategies using multiple measures, thereby highlighting the issue of NBS scalability.

Domaines: Ingénierie de l'environnement; Géomorphologie; Hydrologie; Construction hydraulique; Risques

O Bokhove, M Kelmanson, T Kent, Guillaume Piton, J.-M Tacnet. Using 'flood-excess volume' to assess and communicate flood-mitigation schemes. Evidence Based Decisions for UK Landscapes - Rural and Urban Land use, Coastal and Inland Waters, Sep 2018, Cambridge, United Kingdom. ⟨hal-01983244⟩