Nature-Based Solutions for Flood Mitigation and Soil Conservation in a Steep-Slope Olive-Orchard Catchment (Arquillos, SE Spain)

Abstract

The frequency and magnitude of flash floods in the olive orchards of southern Spain have increased because of climate change and unsustainable olive-growing techniques. Affected surfaces occupy >85% of the rural regions of the Upper Guadalquivir Basin. Dangerous geomorphic processes record the increase of runoff, soil loss and streamflow through time. We report on ripple/dune growth over a plane bed on overland flows, deep incision of ephemeral gullies in olive groves and rock-bed erosion in streams, showing an extraordinary sediment transport capacity of sub-daily pluvial floods. We develop a novel method to design optimal solutions for natural flood management and erosion risk mitigation. We adopt physical-based equations and build a whole-system model that accurately reproduces the named processes. The approach yields the optimal targeted locations of nature-based solutions (NbSs) for active flow-control by choosing the physical-model parameters that minimise the peak discharge and the erosion-prone area, maximising the soil infiltration capacity. The sub-metric spatial resolution used to resolve microtopographic features of terrains/NbS yields a computational mesh with millions of cells, requiring a Graphics Processing Unit (GPU) to run massive numerical simulations. Our study could contribute to developing principles and standards for agricultural-management initiatives using NbSs in Mediterranean olive and vineyard orchards.

Technological Advances to Rescue Temporary and Ephemeral Wetlands: Reducing Their Vulnerability, Making Them Visible

“…In this context, we recently showed that highly resolved computational fluid dynamics simulations of hydrological and hydraulic processes, using the 2D Saint-Venant equations, yield the optimal location of NbS (e.g., natural and artificial wetlands, vegetal cover, riparian restoration, gravels seeding in streambeds, etc.) to provide the most benefits for minimising the water discharges and the erosion-prone area, maximising the soil infiltration capacity [46]. Consequently, the location and restoration of extinct wetlands, or even the artificial creation of new ones, are of great importance for adaptation to climate change since they reduce the risk of flooding and minimise the effects of drought.…”

“…In the current context of adaptation to climate change, this technique can be a handy, inexpensive, and agile resource for managers to conserve this type of ecosystem and their biodiversity. Furthermore, the recovery and restoration of wetlands could mitigate other types of threats related to extreme climate events by reducing the risk of flooding, especially in towns surrounded by agricultural areas with null soil protection, and favours the recharge of aquifers [46].…”