Evidence of an emerging levee failure mechanism causing disastrous floods in Italy

Abstract

A levee failure occurred along the Secchia River, Northern Italy, on 19 January 2014, resulting in flood damage in excess of $500 million. In response to this failure, immediate surveillance of other levees in the region led to the identification of a second breach developing on the neighboring Panaro River, where rapid mitigation efforts were successful in averting a full levee failure. The paired breach events that occurred along the Secchia and Panaro Rivers provided an excellent window on an emerging levee failure mechanism. In the Secchia River, by combining the information content of photographs taken from helicopters in the early stage of breach development and 10 cm resolution aerial photographs taken in 2010 and 2012, animal burrows were found to exist in the precise levee location where the breach originated. In the Panaro River, internal erosion was observed to occur at a location where a crested porcupine den was known to exist and this erosion led to the collapse of the levee top. This paper uses detailed numerical modeling of rainfall, river flow, and variably saturated flow in the levee to explore the hydraulic and geotechnical mechanisms that were triggered along the Secchia and Panaro Rivers by activities of burrowing animals leading to levee failures. As habitats become more fragmented and constrained along river corridors, it is possible that this failure mechanism could become more prevalent and, therefore, will demand greater attention in both the design and maintenance of earthen hydraulic structures as well as in wildlife management.

Burrowing Invasive Species: An Unquantified Erosion Risk at the Aquatic‐Terrestrial Interface

“…This reflects the fact that the burrowing impacts of invasive species tend to be reported as one of a number of detrimental ecosystem impacts, rather than the research focus in the majority of sources. We identified six publications that focus directly on quantifying the impact of invasive burrowers on slope stability or erosion at aquatic margins, but all of these linked burrowing with increased instability and/or erosion (Aman & Wilson Grimes, ; Davidson & de Rivera, , ; Faller et al, ; Orlandini et al, ; Rudnick et al, ; Talley et al, ).…”

“…Burrows can extend for up to 5 m in depth and range from simple single‐entrance systems to complex systems with multiple tunnels and entrances at different levels (Washington State Department of Fish and Wildlife, ). Burrowing activity by M. coypus has been linked to the undermining of banks and embankments on irrigation canals (Bertolino & Genovesi, ; Sofia et al, ; Figures e‐g), and burrow‐induced collapse of weakened banks and levees has been linked to devastating flood events (Orlandini et al, ; Panzacchi et al, ). River bank management related to M. coypus has been estimated as in excess of € 1 million per year in Italy (Panzacchi et al, ).…”

Zoogeomorphological behaviours in fish and the potential impact of benthic feeding on bed material mobility in fluvial landscapes

“…Why is this important? Because, despite seminal work (Darwin, 1881), growing theoretical understanding (Steiger and Corenblit, 2012), strong empirical evidence (Phillips, 2009;Rice et al, 2016), technological innovations (Larsen et al, 2017) and societal implications (Orlandini et al, 2015), geomorphologists have not fully assessed or incorporated the role of biological energy in models of geomorphological processes. The relative exclusion of biological processes from geomorphological thinking may have happened for a complex mixture of reasons, including historic accident, propinquity, key gatekeeper personalities, lack of conceptual frameworks and the inertia of conventional thought (Johnson, 2002).…”

Prospects for crowdsourced information on the geomorphic ‘engineering’ by the invasive Coypu (Myocastor coypus)

“…The presence of surface erosion can significantly reduce the integrity of the banks, causing in some cases bank failure through a combination of hydraulic and gravitation forces (Orlandini et al, 2015). Furthermore, if burrows are present (Figure 2(e)), the ground may collapse when subjected to the weight of heavy objects on the surface (such as vehicles and farm machinery, Figure 2(f)).…”

“…On the other, the information available about the damages is limited to local knowledge, grey literature, and maintenance reports. Only a few studies have been made to model and quantify the evidence and the effect of animal-induced erosion along channel networks (Bayoumi and Meguid, 2011;Orlandini et al, 2015). In northern Italy, irrigation is managed collectively through farmers' associations, and irrigation canals are highly segmented and separated (Massarutto, 2000).…”