Assessment of Intra-Annual and Inter-Annual Variabilities of Soil Erosion in Crete Island (Greece) by Incorporating the Dynamic “Nature” of R and C-Factors in RUSLE Modeling

Abstract

Under the continuously changing conditions of the environment, the exploration of spatial variability of soil erosion at a sub-annual temporal resolution, as well as the identification of high-soil loss time periods and areas, are crucial for implementing mitigation and land management interventions. The main objective of this study was to estimate the monthly and seasonal soil loss rates by water-induced soil erosion in Greek island of Crete for two recent hydrologically contrasting years, 2016 (dry) and 2019 (wet), as a result of Revised Universal Soil Loss Equation (RUSLE) modeling. The impact of temporal variability of the two dynamic RUSLE factors, namely rainfall erosivity (R) and cover management (C), was explored by using rainfall and remotely sensed vegetation data time-series of high temporal resolution. Soil, topographical, and land use/cover data were exploited to represent the other three static RUSLE factors, namely soil erodibility (K), slope length and steepness (LS) and support practice (P). The estimated rates were mapped presenting the spatio-temporal distribution of soil loss for the study area on a both intra-annual and inter-annual basis. The identification of high-loss months/seasons and areas in the island was achieved by these maps. Autumn (about 35 t ha−1) with October (about 61 t ha−1) in 2016, and winter (about 96 t ha−1) with February (146 t ha−1) in 2019 presented the highest mean soil loss rates on a seasonal and monthly, respectively, basis. Summer (0.22–0.25 t ha−1), with its including months, showed the lowest rates in both examined years. The intense monthly fluctuations of R-factor were found to be more influential on water-induced soil erosion than the more stabilized tendency of C-factor. In both years, olive groves in terms of agricultural land use and Chania prefecture in terms of administrative division, were detected as the most prone spatial units to erosion.

Linking Soil Erosion Modeling to Landscape Patterns and Geomorphometry: An Application in Crete, Greece

“…In Greece, the farming practice for areas exceeding 10% slope is the cultivation along or diagonal to the contour (cross slope contour farming) in order to conserve rainwater and to reduce soil losses [19]. In Crete, the main conservation support practices are contour farming, stone walls, and grass margins [1]; thus, these three types of support practices were considered to estimate the P-factor. The following table (Table 1) summarizes the input dataset required for RUSLE model.…”

“…Both slope length and steepness are proportional to erosion. Consequently, increases in L and S lead to higher runoff velocities and higher soil loss rates [1]. These topographic parameters are so sensitive to soil loss that a minor miscalculation could lead to inaccurate assessment of the overall soil erosion rates.…”

“…Although this topographic factor is one of the principal factors for the RUSLE model, ground-based measurement data are usually unavailable. As an alternative to ground-based measurement, the LS-factor can be estimated using digital elevation models (DEMs) using geographic information system software [1,21].…”

“…Soil erosion is one of the most important worldwide issues, which is caused mainly by natural factors (wind, water, and snow) and can be accelerated by anthropogenic activities [1], exceeding in some cases the amount of soil regeneration [2]. Accordingly, in some parts of the Mediterranean region, erosion is reaching an irreversible level, while in other places no more soil is left.…”

A Quantile Mapping Method to Fill in Discontinued Daily Precipitation Time Series

“…The steep orography has a strong effect on the precipitation regimen, with large orographic precipitation effects to be observed [17][18][19][20] that, in combination with its location within the Mediterranean, have resulted in numerous heavy precipitation events that were followed by serious flooding events, such as those which occurred in the Giofiros region in 1994 [17,21], in the Almirida region in 2007 [22,23], as well as February 2019 s extensive flooding in the Chania prefecture [24] and floods in the southern parts of the island [25]. Recent findings have indicated that the region's precipitation regime facilitates rainfall induced soil erosivity to a larger extend than was previously thought [26,27]. From a hydrogeological perspective, the island is mainly composed of pre-alpine and alpine carbonate formations and neogene and quaternary (alluvial) sediments which expedite water penetration; hence, the region exhibits limited surface water resources [28].…”