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Item type:Publication, The effect of natural infrastructure on water erosion mitigation in the Andes(2021-07-28)Soil erosion by water is affecting natural and anthropogenic environments through its impacts on water quality and availability, loss of soil nutrients, flood risk, sedimentation in rivers and streams, and damage to civil infrastructure. Sustainable management aims to avoid, reduce and reverse soil erosion and can provide multiple benefits for the environment, population, and livelihoods. We conducted a systematic review of 121 case studies from the Andes to answer the following questions: (1) Which erosion indicators allow us to assess the effectiveness of natural infrastructure? (2) What is the overall impact of working with natural infrastructure on on-site and off-site erosion mitigation? and (3) Which locations and types of studies are needed to fill critical gaps in knowledge and research? Three major categories of natural infrastructure were considered: protective vegetation, soil and water conservation measures, and adaptation measures that regulate the flow and transport of water. From the suite of physical, chemical and biological indicators commonly used in soil erosion research, two indicators were particularly relevant: soil organic carbon (SOC) of topsoil, and soil loss rates at the plot scale. In areas with protective vegetation and/or soil and water conservation measures, the SOC of topsoil is –on average– 1.3 to 2.8 times higher than in areas under traditional agriculture. Soil loss rates in areas with natural infrastructure were reported to be 38 % to 54 % lower than rates measured in untreated croplands. Further research is needed to evaluate whether the reported effectiveness holds during extreme events related to, for example, El Niño–Southern Oscillation. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, The effect of natural infrastructure on water erosion mitigation in the Andes(Copernicus Publications, 2022-02-28)Abstract. To expand the knowledge base on natural infrastructure for erosion mitigation in the Andes, it is necessary to move beyond case by case empirical studies to comprehensive assessments. This study reviews the state of evidence on the effectiveness of interventions to mitigate soil erosion by water and is based on Andean case studies published in gray and peer-reviewed literature. Based on a systematic review of 118 case studies from the Andes, this study addressed the following research questions. (1) Which erosion indicators allow us to assess the effectiveness of natural infrastructure? (2) What is the overall impact of working with natural infrastructure on on-site and off-site erosion mitigation? (3) Which locations and types of studies are needed to fill critical gaps in knowledge and research? Three major categories of natural infrastructure were considered: restoration and protection of natural vegetation, such as forest or native grasslands, forestation with native or exotic species and implementation of soil and water conservation measures for erosion mitigation. From the suite of physical, chemical and biological indicators commonly used in soil erosion research, two indicators were particularly relevant: soil organic carbon of topsoil and soil loss rates at plot scale. The protection and conservation of natural vegetation has the strongest effect on soil quality, with 3.01±0.893 times higher soil organic carbon content in the topsoil compared to control sites. Soil quality improvements are significant but lower for forestation and soil and water conservation measures. Soil and water conservation measures reduce soil erosion to 62.1 % ± 9.2 %, even though erosion mitigation is highest when natural vegetation is maintained. Further research is needed to evaluate whether the reported effectiveness holds during extreme events related to, for example, El Niño–Southern Oscillation. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Spatial variation in specific sediment yield along the Peruvian western Andes(Elsevier BV, 2022-10-22)The tropical Andes has been less studied in terms of erosion processes in comparison to other major mountain ranges in the world. Environmental gradients are steepest along the western flank of the Andes that is characterized by marked differences in vegetation, rough topography with deeply incised canyons, and highly variable and extreme precipitation patterns. Previous efforts mostly focused on sediment fluxes in large rivers draining to e.g. the Amazon basin while small to medium-sized rivers such as the ones flowing towards the Pacific Ocean have been relegated. They highlighted the link between sediment yield, anthropogenic and natural factors, e.g. climate, topography, river runoff, lithology and vegetation cover. In this study, we identified the spatial patterns of specific sediment yield along the western slopes of the Peruvian Andes between 3° and 13° S latitude for 21 catchments. We collected and analysed data from 22 environmental factors to elucidate their importance on spatially varying sediment yield. The sediment load was derived from gauging stations, reservoir sedimentation and water turbidity over a 30-yr period. The specific sediment yield varies strongly along the Peruvian western Andes as a consequence of the spatial variation in climate, topography and land cover controlling sediment production and transport. We reported higher-than-average specific sediment yields for the central part (6°-11°S) with values of 2130 and 2300 t km−2 yr−1 and low and uniform yields of 39 to 551 t km−2 yr−1 in the southern part (11° − 14.5° S). Given the scarcity of data on sediment yield, we included an uncertainty assessment based on bootstrapping approaches as to get a better grasp on the potential range of specific sediment yields in the study region. Using statistical techniques including Spearman correlation rank, univariate and multivariate regression analyses, we were able to determine the importance of the 22 environmental variables on the specific sediment yield. About 55 % of the observed variance can be explained by river discharge (Q90) and river steepness index (ks50). By adding an anthropogenic variable based on land cover, the explained variance in SSY increases up to 63 %, however, the effects of land cover on specific sediment yield are not clear because of spurious correlation between land cover, river discharge and topography. Our study therefore provides important new insights in the ongoing scientific debate on sediment yield variability in the western Andes. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Quantifying Geomorphic Change in Andean River Valleys Using UAV-PPK-SfM Techniques: An Example from the Western Peruvian Andes(Elsevier B.V., 2023-08-15)The western Peruvian region is prone to erosion and geomorphic change. Extreme precipitation events lead to rapid change in river channel and floodplain morphology due to bank erosion and debris flows delivering detrital material to the fluvial system. Monitoring geomorphic events and their associated topographic changes at high spatial and temporal resolutions remains a challenge. Here, we used an Uncrewed Aerial Vehicle - Post-Processing Kinematic - Structure from Motion (UAV-PPK-SfM) approach that includes co-registration of point clouds by using relative Ground Control Points (GCPs). This workflow adjusts each elevation model to a reference model using invariant features that did not change their position or form over time. We applied this technique to monitor landscape change (2019–2021) in an area of 0.3 km2 located in the Cañete River basin. Our results showed that a minimum observable elevation change of 0.56 m (95 % confidence interval) can be achieved using this workflow, beyond which an actual elevation change can be separated from systematic error. Using object-based classification techniques on the aerial images, we separated geomorphic dynamics from land cover changes. This allowed us to isolate the effect of geomorphic processes, and quantify rates related to gully erosion, river scouring, bank erosion, and sediment deposition. Within the study area, a hotspot of geomorphic change corresponded to an ephemeral tributary channel. The gully channel incising an alluvial fan is highly dynamic, showing bank erosion of 0.75 to 3.2 m and net export of 37 m3 of sediment in the 25-month study period. Given that the monitoring period did not include high intensity rainfall events, the study illustrates how geomorphic activity in ungauged Andean river basins, such as the Cañete valley, may be considerably underestimated in literature. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Data limitations in developing countries make river restoration planning challenging. Study case of the Cesar River, Colombia(Elsevier B.V., 2025-01-01)Past research has mapped the limitations of water quality data in developing countries. This contribution reports a detailed assessment of the status of water quality data of the Cesar River, one of the main tributaries of the Magdalena River, which is regarded as the largest river system in Colombia. Our assessment indicates that the data is limited (in terms of length of record and resolution spatial) and exhibits significant information gaps, and that it is collected through a network of very sparse ground stations with deficient density. Subnational permissible limits for the five main water quality parameters (i.e., pH, TP, TN, DO, TSS) determine that water has reached worrisome levels of pollution. The data limitations does not allow for establishing the influence of natural (e.g., soil erosion) or anthropogenic processes such as wastewater discharges and in-channel sand mining into water quality. Since Colombia is a member of the Pacific Alliance and the Organisation for Economic Co-operation and Development (OECD) the associated supranational water quality regulatory frameworks are analyzed as they may guide the permissible limits and targets in the coming years. A freely accessible database of water quality observations between the years 2004–2020 of the Cesar River accompanies this contribution. We believe that it potentially constitutes a scientific input to plan for restoring the ecosystem services of the Cesar. We also believe this study depicts a representative case of the status of several rivers from the Latin American sphere and other developing countries.3 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Gully erosion assessment in mountainous regions: a RUSLE-based methodology for the Central Peruvian Andes(Taylor and Francis Ltd., 2026)Soil erosion is a significant global threat, with gully erosion forming deep hillside channels that substantially contribute to sediment yield. While erosion is often assessed using models like the Revised Universal Soil Loss Equation (RUSLE), its limitation to only consider surface erosion, avoiding severe erosion processes, led us to develop RUSLEad, an adapted version for gully erosion. The method integrates the Topographic Wetness Index (TWI) and a region-specific sediment delivery ratio in its formulation and includes generalized likelihood uncertainty estimation for model validation. Our pilot study is a basin of 13 km2 located in the Central Peruvian Andes. There, we collected detailed topographic and soil data. Chosen for its cost-effectiveness and data accessibility, RUSLEad produced erosion maps and average sediment yield estimates, and identified erosion hotspots. This method, applicable to similar terrain elsewhere, supports Peru’s Climate Change Strategy 2050 by informing gully control and contributing to prioritizing potential remediation efforts.