Reconstruction of Seasonal Net Erosion in a Mediterranean Landscape (Alento River Basin, Southern Italy) over the Past Five Decades

Abstract

In the low Mediterranean basin, late spring and autumn rainfall events have the potential to increase discharge and transport substantial amounts of sediment soil (that is, the net soil erosion from a watershed). For the Alento River Basin (ARB), located in the low Tyrrhenian coast of Italy, we estimated changes of net erosion as dependent on the seasonality of antecedent soil moisture and its control on rainfall-runoff and erosivity. Based on rainfall and runoff erosivity sub-models, we developed a simplified model to evaluate basin-wide sediment yields on a monthly basis by upscaling point rainfall input. For the period 1951–2018, the reconstruction of a time series of monthly net erosion data indicated a decreasing trend of the sediment yield after 1991. Revegetation and land abandonment that occurred in the last decades can explain such a decrease of net erosion, which occurred even when rainfall erosivity increased. This response, obtained at the basic scale, does not exclude that rapidly developing mesoscale convective systems, typically responsible for the heaviest and most destructive rainfall events in the ARB, can affect small catchments, which are the most vulnerable systems to storm-driven flash floods and soil erosion hazards during soil tilling in spring and at beginning of autumn.

Mitigating Source Water Risks with Improved Wildfire Containment

“…Despite these approximations, the resulting turbidities-which averaged 309, 516, and 1181 NTU for the 2, 10, and 100-year rainfall erosivity, respectively-align well with common observations in the region of post-fire turbidities between 100 and 1000 NTU and occasional observations >1000 NTU [15,48,89]. The assumption that storm load is an equal division of annual load does not account for the substantial intra-annual variability in storm characteristics [15,83,90], seasonal trends in runoff and erosion [91], nor the interannual variability in the frequency of storms with sufficient intensity to cause erosion [34,66]. Similarly, unaccounted for variability in daily flow volume influence the vulnerability of the water source.…”

Urban stormwater characterization, control, and treatment

“…With these data, a net erosion model was developed. The results highlighted that sediment fluctuations in the study area are attributed to climatic oscillations and that revegetation of land area reduces net soil erosion (Diodato & Bellocchi, 2019).…”

A framework for modelling emergent sediment loss in the Ombrone River Basin, central Italy

“…This has allowed the identification of concepts for the development of parsimonious modelling solutions for sediment load assessment of river systems [44][45][46][47]. Given the issue of assessing erosive sediment by complex models in recognition of the detailed input for the historical period, we arranged a parsimonious erosion model adapted to the annual scale from the original algorithms of Foster et al [48] and Thornes [49] because they provide an interpretation of empirically determined factors shaping active erosional landscapes in basin areas based on the parsimonious balance between driving and resisting forces in the sediment budget [50,51]. The driving forces are essentially simplified to proxies or indicators or rainfall and runoff erosivity associated with splash and transport erosion, respectively.…”

“…The driving forces are essentially simplified to proxies or indicators or rainfall and runoff erosivity associated with splash and transport erosion, respectively. This simplification seems to be adequate for the generation of basin-wide annual outputs, while it may not be fully applicable for the generation of monthly outputs, as seasonal effects become prominent due to the concurrence of rainfall erosivity with different seasonal conditions of soil erodibility [50,51]. Resisting forces are expressed as an exponential function of the fraction of vegetation cover in the basin, as erosion rates show a steep decay compared to that of a bare soil as plant cover increases [52].…”