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This study has evaluated the runoff and erosion rates in torrents of Southern Italy, two forested headwaters with very similar climatic, hydrological and geomorphological characteristics, in one headwater, 15 check dams were installed in the mid-1950s, while the other is not regulated with engineering works. To this aim, the hydrological variables have been modeled over 15 years after check dam installation using the HEC-HMS (Hydrologic Engineering Center-Hydrologic Modeling System) model coupled to the MUSLE (Modified Universal Soil Loss Equation) equation. The model simulations have shown that check dams have not played a significant role in reducing the surface runoff compared to the unregulated torrent, in both catchments, the well-developed forest cover determined very low runoff coefficients (lower than 0.3%) with a scarce runoff generation capacity. Additionally, the reduction in peak flow due to the check dams was not significant, on average −7.4% compared to the unregulated headwater. Check dams have retained sediments for about 8–10 years after their installation, reducing erosion by about 35%, although soil loss was much lower than the tolerance limit in both catchments. After the sediment retention capacity of the dam sediment wedge was depleted, the sediment yield in the regulated torrent was even higher (by about 20%) compared to the unregulated catchment. Overall, the study has shown that the use of check dams as a catchment management strategy of forested headwaters under semi-arid Mediterranean conditions should be considered with caution, since the structures could be ineffective to reduce water and sediment flows during floods or, in some cases, check dams may increase erosion rates.

[Abstract] Forest fires and post-fire practices influence sediment connectivity (SC). In this study, we use the ‘aggregated index of connectivity’ (AIC) to assess SC in five Mediterranean catchments (198–1090 ha) affected by a wildfire in 2012 in south-eastern Spain. Two temporal scenarios were considered, immediately after the fire and before post-fire management, and 2 years after the fire including all practices (hillslope barriers, check-dams, afforestation, salvage logging and skid trails). One LiDAR (light detection and ranging)-derived digital elevation model (DEM, 2 m × 2 m resolution) was generated, per scenario. The five catchment outlets were established as the computation target (AICоᴜᴛ), and structural and functional SC were calculated. Index outputs were normalized to make the results of the non-nested catchments comparable (AICɴ₋оᴜᴛ). The output analysis includes the SC distribution along the catchments and at local scale (929 sub-catchments, 677 in the burned area), the hillslope and channel measures' effect on SC, and a sedimentological analysis using observed area-specific sediment yield (SSY) at 10 new (built after post-fire practices) concrete check-dams located in the catchments (SSY = 1.94 Mg ha⁻¹ yr⁻¹; σ = 1.22). The catchments with more circular shapes and steeper slopes were those with higher AICɴ₋оᴜᴛ. The structural SC maps – removing the rainfall erosivity influence – allowed evaluating the actual role played by the post-fire practices that reduced SC (x̅ = − 1.19%; σ = 0.41); while functional SC was linked to the actual change of SC (x̅ = + 5.32%; σ = 0.62). Hillslope treatments resulted in significant changes on AICɴ₋оᴜᴛ at sub-catchment scale with certain disconnectivity. A good and positive correlation was found between the SSY and the changes of AICɴ₋оᴜᴛ. However, the coarse DEM resolution explained the lack of effect of the rock check-dams – located on the secondary channels – on AICɴ₋оᴜᴛ. AICɴ₋оᴜᴛ proved to be a useful tool for decision making in post-fire restoration, but an optimal input data is still necessary to refine calculations. European Cooperation in Science and Technology; CA18135 Gobierno de Castilla-la Mancha; Sbply/16/180501/ 000109 This study was supported by funds provided to the VIS4FIRE Spanish R&D project (RTA2017-00042-C05-00) co-funded by the “Instituto Nacional de Investigación y Tecnología Agraria” (INIA) and FEDER programme. This study was done in the frame of the European Cooperation in Science and Technology (COST) action CA18135 ‘FIRElinks’ (Fire in the Earth System:Science & Society). J. González-Romero holds a scholarship (Sbply/16/180501/000109) from the Regional Government of Castilla-La Mancha/European Social Fund (ESF, EU).

ispartof: EARTH SURFACE PROCESSES AND LANDFORMS vol:45 issue:13 pages:3250-3279 status: published

Lake Elton is located east of the Volga River in Russia and covers an area of 155¿km2. The hydrological system of the Lake and its surroundings are extremely vulnerable to climate change and human interference, but available local and regional information is sparse. Utilising climate data from 1987 to 2009 and surface albedo readings from the MODerate resolution Imaging Spectroradiometer satellite since 2000, this study analyses Lake degradation processes since 2005. Lake surface albedo analysis indicates that during the past 6¿years, lake albedo has increased dramatically from average peak values of 0·14 to 0·40. In addition, air temperature has increased by 2¿°C, and annual precipitation has decreased by 40 per cent. Moreover, human intervention in the area has increased environmental pressure on the Lake, causing a reduction of runoff inflow because of water capture, use of check-dams and water-harvesting systems. The results of the study show that, under current conditions, the Lake surface albedo is likely to remain high as compared with previous observations. The current trend implies an average 2 per cent per year increase in future annual albedo, with a maximum possible increase of 4 per cent up to a steady state of salt-crust albedo values

Soil erosion in southeast Spain is a complex process due to strong interactions between biophysical and human components. Significant progress has been achieved in the understanding of soil hydrological behavior, despite the fact that most investigations were focused on the experimental plot scale. Although experimental plots allow exploring the effect of multiple biophysical and anthropogenic factors, they provide limited insights in the combined effect of all factors acting together at the landscape scale. In this study, area-specific sediment yields (SSY) have been estimated based on the volume of sediment trapped behind 36 check dams in the southeast of Spain. Low SSY-values were reported (mean = 1.40 t ha(-1) year(-1): median = 0.61 t ha(-1) year(-1)), SSY variability could be explained for 67% by catchment characteristics such as drainage area, soil characteristics, land cover, average catchment slope, and annual rainfall. The low SSY values are probably caused by the agricultural abandonment that occurred over the past decades and allowed the recovery of natural vegetation. Furthermore, our results suggest that the soils have eroded in the past to such an extent that nowadays not much sediment is detached by overland flow due to residual enrichment of clay and stones. Also, sediment is to a large extent trapped locally in the catchment, as indicated by the negative relationship between SSY and catchment area. (C) 2011 Elsevier B.V. All rights reserved.

29 Pags.- 6 Tabls.- 6 Figs. This article belongs to a special issue of Catena titled "Geoecology in Mediterranean mountain areas. Tribute to Professor José María García Ruiz". The definitive version is available at: http://www.sciencedirect.com/science/journal/03418162, Understanding how organic carbon (OC) moves with sediments along the fluvial system is crucial to determining catchment scale carbon budgets and helps the proper management of fragile ecosystems. Especially challenging is the analysis of OC dynamics during fluvial transport in heterogeneous, fragile, and disturbed environments with ephemeral and intense hydrological pulses, typical of Mediterranean conditions. This paper explores the catchment scale OC redistribution by lateral flows in extreme Mediterranean environmental conditions, from a geomorphological perspective. The study area is a catchment (Cárcavo) in SE Spain with a semiarid climate, erodible lithologies, and shallow soils, which is highly disturbed by agricultural terraces, land levelling, reforestation, and construction of check-dams. To increase our understanding of catchment scale OC redistribution induced by erosion, we studied in detail the subcatchments of eight check-dams distributed along the catchments main channel. We determined 137Cs, physicochemical characteristics, and the OC pools of the catchment soils and sediments deposited behind each check-dam, performed spatial analysis of catchment properties and buffer areas around the check-dams, and carried out geomorphological analysis of the slope-channel connections. The soils showed very low total organic carbon (TOC) values, oscillating between 15.2 and 4.4 g kg− 1 for forest and agricultural soils, respectively. Sediments mobilized by erosion were poor in TOC (6.6 ± 0.7 g kg– 1) compared to the eroded (forest) soils, and the redistribution of OC through the catchment, especially of the mineral associated organic carbon (MAC) pool, showed the same pattern as clay particles and 137Cs. The TOC erosion rates estimated for the Cárcavo watershed are relatively low (0.031 ± 0.03 Mg ha− 1 y− 1) but similar to those reported for subhumid Mediterranean catchments that are less fragile and more conducive to plant growth. The TOC erosion/total erosion ratio was lower (0.06%) than other estimates, although the average OC concentration of the sediments was higher than that of the agricultural soils of the catchment, underlining the problem of maintaining sustainable soil OC contents. The OC in deposited sediments came not only from surface erosion processes, but also from deeper soil or sediment layers mobilized by concentrated erosion processes. Sediment richer in OC came from the surface soil of vegetated (reforested) areas close and well connected to the channels. Subcatchments dominated by laminar erosion processes showed a TOC erosion/total erosion ratio that was two times higher than that of subcatchments dominated by concentrated flow erosion processes. The lithology, soils, and geomorphology exert a more important control on OC redistribution than land use and vegetation cover in this geomorphologically very active catchment., This work was financially supported by the projects ADAPT (CGL2013-42009-R) and DISECO (CGL2014-55-405-R) from the Spanish Government, National Plan of Science; the project CAMBIO (18933/JLI/13) of the Seneca Foundation, Regional Government of Murcia (Spain); and the project SOGLO (P7/24 IAP BELSPO) from the Belgian Government. Joris de Vente was supported by a ‘Ramón y Cajal’ grant (RYC-2012-10375).

Lake Elton is located east of the Volga River in Russia and covers an area of 155¿km2. The hydrological system of the Lake and its surroundings are extremely vulnerable to climate change and human interference, but available local and regional information is sparse. Utilising climate data from 1987 to 2009 and surface albedo readings from the MODerate resolution Imaging Spectroradiometer satellite since 2000, this study analyses Lake degradation processes since 2005. Lake surface albedo analysis indicates that during the past 6¿years, lake albedo has increased dramatically from average peak values of 0·14 to 0·40. In addition, air temperature has increased by 2¿°C, and annual precipitation has decreased by 40 per cent. Moreover, human intervention in the area has increased environmental pressure on the Lake, causing a reduction of runoff inflow because of water capture, use of check-dams and water-harvesting systems. The results of the study show that, under current conditions, the Lake surface albedo is likely to remain high as compared with previous observations. The current trend implies an average 2 per cent per year increase in future annual albedo, with a maximum possible increase of 4 per cent up to a steady state of salt-crust albedo values

Extensive land use changes have occurred in many areas of SE Spain as a result of reforestation and the abandonment of agricultural activities. Parallel to this the Spanish Administration spends large funds on hydrological control works to reduce erosion and sediment transport. However, it remains untested how these large land use changes affect the erosion processes at the catchment scale and if the hydrological control works efficiently reduce sediment export. A combination of field work, mapping and modelling was used to test the influence of land use scenarios with and without sediment control structures (check-dams) on sediment yield at the catchment scale. The study catchment is located in SE Spain and suffered important land use changes, increasing the forest cover 3-fold and decreasing the agricultural land 2·5-fold from 1956 to 1997. In addition 58 check-dams were constructed in the catchment in the 1970s accompanying reforestation works. The erosion model WATEM-SEDEM was applied using six land use scenarios: land use in 1956, 1981 and 1997, each with and without check-dams. Calibration of the model provided a model efficiency of 0·84 for absolute sediment yield. Model application showed that in a scenario without check dams, the land use changes between 1956 and 1997 caused a progressive decrease in sediment yield of 54%. In a scenario without land use changes but with check-dams, about 77% of the sediment yield was retained behind the dams. Check-dams can be efficient sediment control measures, but with a short-lived effect. They have important side-effects, such as inducing channel erosion downstream. While also having side-effects, land use changes can have important long-term effects on sediment yield. The application of either land use changes (i.e. reforestation) or check-dams to control sediment yield depends on the objective of the management and the specific environmental conditions of each area., This work was financially supported by a research project of the Fundación Instituto Euromediterráneo del Agua (CE) and by the Spanish Ministry of Science and Education through the projects CANOA CGL2004- 04 949-C02-01; PROBASE CGL2006-11 619 and ERCO CGL2007-62 590/BTE. The first author was financially supported by an I3P postdoc contract CSIC-CE and a “Ramón y Cajal” contract from the Spanish Ministry of Science and Education. Gonzalo G. Barberá also was supported by I3P postdoc contract. Joris de Vente was supported by a Seneca (Region of Murcia Government) foreign researchers grant and through a contract in the integrated project DESIRE of the EU FP6 037 046 (GOCE).