1,721,361 research outputs found
Modeling and upscaling plot-scale soil erosion under mediterranean climate variability
No full textSoil erosion is an issue in the Mediterranean slopes. Erosion plots are useful to quantify erosion rates, but data are difficult to scale up to a slope level. Moreover, short observational frameworks are generally established, making it difficult to represent multi-year fluctuations. This paper deals with the potential of parsimonious modelling to upscale plot erosion (~23 m2) at Monte Pino Met European Research Observatory (South Italy) from 2001 to 2006. Under the assumption that the slope is fractal and contains plots, monthly gross soil erosion was modeled by lumping together the erosivity factor (runoff component), Normalized Difference Vegetation Index (vegetation cover factor), and the spatial scale dependence (slope length factor). This model was applied to reconstruct monthly gross soil erosion rates for the period of 1986–2006, for which hydrological inputs were available with sufficient detail. Pronounced interannual variations, with two distinct patterns, were observed: increasing rates of erosion were visible in 1995–2006 (peaking in November 1997, 50 Mg·ha−1·month−1), while in previous years only a few peaks slightly exceeded the average of the whole period (1 Mg·ha−1·month−1). Hydrological conditions indicate that important erosional processes have been triggered during low-frequency, short rainfall events occurring in spring–summer (e.g., May 2001, June 2003), or during longer, less intense events occurring in autumn–winter (e.g., November 1997) seasons. It is likely that increased precipitation amounts associated with more frequent convective storms created conditions for higher energy events triggering erosion. For the recent warm period, investigations at a higher than monthly resolution are required to better assess the seasonal changes of erosion rates and their relationship with soil conservation
Modeling L- and X-band backscattering of wheat and tests over fields of Pampas
No full textA discrete scattering model and a detailed set of ground measurements are used to simulate the backscattering coefficients of wheat fields during the whole growth cycle. Simulations are carried out at L- and X-band, and at HH, VV, and HV polarizations. Wheat fields are located in Pampas (Argentina), and are characterized by low values of plant density. Simulations show that the backscattering coefficient is driven by variations of soil moisture at L-band, particularly for HH polarization, with low vegetation effects. Conversely, the attenuation of vegetation is dominant in producing variations of backscattering coefficients at X-band, particularly for VV polarization. Simulations are compared against experimental data collected over the same Pampas region, using airborne SARAT SAR at L-band and COSMO-SKYMED at X-band. Assuming a surface height standard deviation in a 0.4-0.7 cm range, the simulations generally agree with experimental data, with an RMSE lower than about 2 dB at L-band and X-band, except a limited number of cases. Discrepancies observed in specific conditions are discussed. Overall, the results indicate that a joint use of L- and X-band has a good potential to monitor both soil moisture and vegetation growth
Earth-flow deformation from GPS surveys, Mount Pizzuto earth flow, southern Italy
No full textWe reconstruct the deformational pattern of the Mount Pizzuto earth flow using displacement data derived by successive GPS measurements of a network of 99 monitoring points. 2D strain was computed using displacement data of sets of 4 to 6 points. Results from our analysis indicate that deformation varies along the earth flow with several zones of longitudinal stretching and shortening corresponding to areas where the earth-flow displacement/velocity increase and decrease, respectively. Dilatation and orientation of principal strain axes are consistent with the geometry of deformational structures at the flow surface. © Società Geologica Italiana, Roma 2016
Estimation of earth-slide displacement from GPS-based surface-structure geometry reconstruction: Estimation of earth-slide displacement
No full textWe propose a simple method to estimate the surface displacement of earth slides. It is based on the assumptions that earth slides move by sliding along a discrete basal-slip surface and extensional structures, which commonly characterize their depletion zone, completely accommodate the occurred displacement. The proposed method is based on the reconstruction of the cross-sectional geometry of structures crossed by an arbitrary chosen longitudinal profile, aligned with the direction of the movement. Structure geometry reconstruction is completed using high-precision GPS survey and the reconstructed geometry is then used as basis to measure horizontal and vertical components of the displacement accommodated by each single extensional structure. Total horizontal and vertical earth-slide displacements are calculated as the sum of displacements accumulated at each single structure. We test the method at the Summonte earth slide in southern Italy using real-time kinematic GPS field mapping. Results from our estimation were validated considering a single displacement vector derived from the direct and indirect measurement of the position of an isolated tree located below the extensional zone of the slide. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature
- …
