Relationship of Weather Types on the Seasonal and Spatial Variability of Rainfall, Runoff, and Sediment Yield in the Western Mediterranean Basin

Abstract

Rainfall is the key factor to understand soil erosion processes, mechanisms, and rates. Most research was conducted to determine rainfall characteristics and their relationship with soil erosion (erosivity) but there is little information about how atmospheric patterns control soil losses, and this is important to enable sustainable environmental planning and risk prevention. We investigated the temporal and spatial variability of the relationships of rainfall, runoff, and sediment yield with atmospheric patterns (weather types, WTs) in the western Mediterranean basin. For this purpose, we analyzed a large database of rainfall events collected between 1985 and 2015 in 46 experimental plots and catchments with the aim to: (i) evaluate seasonal differences in the contribution of rainfall, runoff, and sediment yield produced by the WTs; and (ii) to analyze the seasonal efficiency of the different WTs (relation frequency and magnitude) related to rainfall, runoff, and sediment yield. The results indicate two different temporal patterns: the first weather type exhibits (during the cold period: autumn and winter) westerly flows that produce the highest rainfall, runoff, and sediment yield values throughout the territory; the second weather type exhibits easterly flows that predominate during the warm period (spring and summer) and it is located on the Mediterranean coast of the Iberian Peninsula. However, the cyclonic situations present high frequency throughout the whole year with a large influence extended around the western Mediterranean basin. Contrary, the anticyclonic situations, despite of its high frequency, do not contribute significantly to the total rainfall, runoff, and sediment (showing the lowest efficiency) because of atmospheric stability that currently characterize this atmospheric pattern. Our approach helps to better understand the relationship of WTs on the seasonal and spatial variability of rainfall, runoff and sediment yield with a regional scale based on the large dataset and number of soil erosion experimental stations.

Features of weather types involving heavy rainfall along the southern Spanish Mediterranean

“…A heavy rainfall pattern was apparent, taking into account the type of weather which it generates; in addition, it differs from that reported for other Mediterranean areas including Catalonia (Martin Vide et al, 2008) and Valencia (Camarasa Belmonte et al, 2010, 2014. Therefore, Facing the purely Mediterranean pattern of these sites in the south of Spain (Alboran Sea) there is a contrast between the Atlantic and subtropical patterns, as previously reported by Peña Angulo et al (2020). This duality has been analyzed in general terms in numerous studies (Pons and Soriano, 1994;De Luis et al, 1997;Pascual et al, 2001;Martin Vide, 2004;Llasat et al, 2005;Neppel et al, 2007;Rodrigo and Barriendos, 2008;Lana et al, 2009;Turco and Llasat, 2011;, as has the atmospheric dynamics that is generally involved in such events (Martín et al, 2006;Martin Vide et al, 2008;Camarasa et al, 2010Camarasa et al, , 2018Camarasa et al, , 2020Peña Angulo et al, 2020).…”

An Enhanced Innovative Triangular Trend Analysis of Rainfall Based on a Spectral Approach

“…Furthermore, the western Mediterranean basin is located in the transition between mid-latitudes and a tropical zone, in which atmospheric dynamic interacts with a complex topography to produce a high spatiotemporal variability of rainfall [73]. Based on the coefficient of variation (CV) and the consecutive disparity index (S), [74] showed the strongest influence of the Western Mediterranean Oscillation (WeMO) over locations in which precipitation irregularity was highest (high CV and S values), and vice versa.…”

Effectiveness of Nature-Based Solutions in Mitigating Flood Hazard in a Mediterranean Peri-Urban Catchment

“…The largest flood to date was recorded in October 2006, triggered by rainfall of 102 mm/day (return period 50 years), but older residents report major floods around 1936 and 1966 [15]. In recent years, an increasing number of minors localized flood events have been recorded, triggered by (i) increasing stream discharge driven by urbanization, particularly after construction of the business park according to residents and previous studies [8,15,29]; and (ii) a reduction in the drainage capacity of hydraulic infrastructure (e.g., drains and pipes), caused by siltation driven by soil erosion, mostly from construction sites [32], and by lack of maintenance. Floods are mostly observed at the end of the dry summer season, when short but very intense rainfall events occur, as is typical in the Mediterranean region [33].…”

“…For example, narrowing of some sections of the stream channel above Quinta, performed to facilitate movement of landowners between properties on both margins of the stream, result in overflows and runoff to surrounding areas during high rainfall events, leading to erroneous measurements at the gauging stations (Figure 4a). Land degradation enhanced by construction activities and clear-felling within the catchment may also lead to higher erosion rates and siltation [32], which may temporarily block the flow of water in some hydraulic infrastructures, consequently affecting the peak flows at downstream gauging stations (Figure 4b). Temporary siltation problems may also introduce errors in water height, especially at stream gauging stations with very low discharge, such as that in Espírito Santo (Table 1).…”