Debris flood hazard documentation and mitigation on the Tilcara alluvial fan (Quebrada de Humahuaca, Jujuy province, North-West Argentina)

Abstract

Abstract. For some decades, mass wasting processes such as landslides and debris floods have been threatening villages and transportation routes in the Rio Grande Valley, named Quebrada de Humauhuaca. One of the most significant examples is the urban area of Tilcara, built on a large alluvial fan. In recent years, debris flood phenomena have been triggered in the tributary valley of the Huasamayo Stream and reached the alluvial fan on a decadal basis. In view of proper development of the area, hazard and risk assessment together with risk mitigation strategies are of paramount importance. The need is urgent also because the Quebrada de Humahuaca was recently included in the UNESCO World Cultural Heritage. Therefore, the growing tourism industry may lead to uncontrolled exploitation and urbanization of the valley, with a consequent increase of the vulnerability of the elements exposed to risk. In this context, structural and non structural mitigation measures not only have to be based on the understanding of natural processes, but also have to consider environmental and sociological factors that could hinder the effectiveness of the countermeasure works. The hydrogeological processes are described with reference to present-day hazard and risk conditions. Considering the socio-economic context, some possible interventions are outlined, which encompass budget constraints and local practices. One viable solution would be to build a protecting dam upstream of the fan apex and an artificial channel, in order to divert the floodwaters in a gully that would then convey water and sediments into the Rio Grande, some kilometers downstream of Tilcara. The proposed remedial measures should employ easily available and relatively cheap technologies and local workers, incorporating low environmental and visual impacts issues, in order to ensure both the future conservation of the site and its safe exploitation for inhabitants and tourists.

Sediment Supply and Hydrogeological Hazard in the Quebrada de Humahuaca (Province of Jujuy, Northwestern Argentina)—Rio Huasamayo and Tilcara Area

“…We suggest that local scale works of hydrological risk-reduction, as proposed by Marcato et al [60], should be coupled with basin-scale works to reduce sediment supply. This approach would reduce the hydrogeological hazard and make easier all maintenance operations for the works realized in the downstream reach.…”

“…To solve the problem, Marcato et al [60] proposed the deviation of the Rio Huasamayo before the village, building an artificial channel working as drainage channel. The preservation of Tilcara, however, would not reduce the hydraulic risk, which would only be transferred downstream the Quebrada towards the village of Maimará.…”

“…To eliminate the hydrological risk that characterizes the town of Tilcara, Marcato et al [60] proposed to divert the Rio Huasamayo from the section immediately downstream of the Garganta del Diablo, up to the left bank of the Rio Grande, close to Maimará (a village south of Tilcara). This operation would require excavation in the Pliocene sediments on the left bank of the Rio Huasamayo, to create an artificial channel that would divert it and the construction of an earth-dam to force it to follow the new path, abandoning its natural riverbed.…”

River‐discharge dynamics in the Southern Central Andes and the 1976–77 global climate shift

“…Over the last decade, field observations in NW Argentina have shown that the downstream areas at elevations between 500 and 1000 m have been affected by aggradation processes [ Marcato et al , 2009; Comisión Binacional para el Desarrollo de la Alta Cuenca del Río Bermejo y el Río Grande de Tarija (COBINABE) , ]. We hypothesize that the increase in discharge in the intermediate elevation zone has resulted in increased sediment transfer, which ultimately caused aggradation in lower lying areas, as the fluvial system was overwhelmed by the sustained influx of coarse sediment, causing infrastructural damage and the loss of agricultural land [ Rivelli , ; Cencetti and Rivelli , ; Marcato et al , ].…”

Atmospheric dynamics of extreme discharge events from 1979 to 2016 in the southern Central Andes

“…The intermontane basins of northwestern Argentina constitute part of the Andean tributaries of the La Plata River, the second largest river basin in South America that flows across one of the most populated and economically relevant areas of the continent. In this region, heavy discharge events repeatedly flood agricultural fields and increase demand of infrastructural maintenance (Marcato et al 2009(Marcato et al , 2012de la Torre et al 2011).…”