Runoff and erosion processes are often non-linear and scale dependent, which complicate runoff and erosion modelling at the catchment scale. One of the reasons for scale dependency is the influence ...of sinks, i.e. areas of infiltration and sedimentation, which lower hydrological connectivity and decrease the area-specific runoff and sediment yield. The objective of our study was to model runoff and erosion for a semi-arid catchment using a multi-scale approach based on hydrological connectivity. We simulated runoff and sediment dynamics at the catchment scale with the LAPSUS model and included plot and hillslope scale features that influenced hydrological connectivity. The semi-arid Carcavo catchment in Southeast Spain was selected as the study area, where vegetation patches and agricultural terraces are the relevant sinks at the plot and hillslope scales, respectively. We elaborated the infiltration module to integrate these runoff sinks, by adapting the parameters runoff threshold and runoff coefficient, which were derived from a rainfall simulation database. The results showed that the spatial distribution of vegetation patches and agricultural terraces largely determined hydrological connectivity at the catchment scale. Runoff and sediment yield for the scenario without agricultural terraces were, respectively, a factor four and nine higher compared to the current situation. Distributed hydrological and erosion models should therefore take account of relevant sinks at finer scales in order to correctly simulate runoff and erosion-sedimentation patterns.
A terrace formation model (TERRACE) combined with a longitudinal river profile model (FLUVER) was used to simulate fluvial terrace formation and preservation in the northwest Iberian lower Miño River ...basin under the influence of three tectonic conditions; namely regional vertical uplift, local basin subsidence, and localised differential uplift. The simulation results were compared against mapped terrace altitudes and deposit thicknesses. The best results were achieved by combining all three tectonic factors, indicating that specific terrace formation is a complex interplay of regional and local tectonics. The best fit regional uplift rate of 0.10mka−1 over the past 600ka is higher than the 0.08mka−1 previously estimated for a section farther to the west, which can be attributed to an increase in tectonic uplift from the NW Iberian Atlantic margin toward the east. Local relative subsidence causes sediment accumulation in the local basin and less sedimentation in the fluvial terraces on the surrounding uplifting blocks. Different uplift rates on both sides of the valley caused preservation of unpaired terraces, which are fill terraces on one side of the valley and strath terraces on the other side. Usually, the formation of fill or strath terraces is considered to be only climate-dependent. Our results indicate that local tectonics can be important in the terrace formation and preservation. This suggests that terrace correlations in other river systems, based on deposit thicknesses only, might be over-simplified.
•Numerical modelling exercise backed up with solid field work data•New insights in how tectonics control river terrace formation•New insights in how river terraces may be correlated•Regional timing of tectonic basin activity constrained by fluvial terraces
Land use changes and landscape processes are interrelated and influenced by multiple bio-physical and socio-economic driving factors, resulting in a complex, multi-scale system. Consequently in ...landscapes with active landscape processes such as erosion, land use changes should not be analysed in isolation without accounting for both on-site and off-site effects on landscape processes. To investigate the interactions between land use, land use change and landscape processes, a case study for the Álora region in southern Spain is carried out, coupling a land use change model (CLUE) and a landscape process model simulating water and tillage erosion and sedimentation (LAPSUS). First, both models are run independently for a baseline scenario of land use change. Secondly, different feedbacks are added to the coupled model framework as ‘interaction scenarios’. Firstly effects of land use change on landscape processes are introduced by means of a ‘changed erodibility feedback’. Secondly effects of landscape processes on land use are introduced stepwise: (i) an ‘observed erosion feedback’ where reallocation of land use results from farmers’ perception of erosion features, and (ii) a ‘reduced productivity feedback’ whereby changes in soil depth result in a land use relocation. Quantities and spatial patterns of both land use change and soil redistribution are compared with the baseline scenario to assess the cumulative effect of including each of the interaction mechanisms in the modelling framework.
Overall, total quantities of land use change (areas) and soil redistribution do not differ much for the different interaction scenarios. However, there are important differences in the spatial patterns of both land use and soil redistribution. In addition, by incorporating the perception and bio-physical feedback mechanisms, land use types with stable or increasing acreages are increasingly relocated from their original positions, suggesting a current location on landscape positions prone to soil erosion and sedimentation. Implementing the ‘reduced productivity feedback’ causes most of these effects. Another important outcome is that on-site land use changes trigger major off-site soil redistribution dynamics. These off-site effects are attributed to down slope or downstream changes in sediment transport rates and/or discharge caused by changes in land surface characteristics.
The results of this study provide insight into the interactions between different processes occurring within landscapes and the influence of feedbacks on the development of the landscape. The interaction between processes goes across various spatial and temporal scales, leading to difficulties in linked model representation and calibration and validation of the coupled modelling system.
This study discusses the complex late Holocene evolution of the Gediz River north of Kula, western Turkey, when a basaltic lava flow dammed and filled this river valley. Age control was obtained ...using established and novel feldspar luminescence techniques on fluvial sands below and on top of the flow. This dating constrained the age of the lava flow to 3.0–2.6ka. Two damming locations caused by the lava flow have been investigated. The upstream dam caused lake formation and siltation of the upstream Gediz. The downstream dam blocked both the Gediz and a tributary river, the Geren. The associated lake was not silted up because the upstream dam already trapped all the Gediz sediments. Backfillings of the downstream lake are found 1.5km upstream into the Geren valley. The downstream dam breached first, after which the upstream dam breached creating an outburst flood that imbricated boulders of 10m3 size and created an epigenetic gorge. The Gediz has lowered its floodplain level at least 15m since the time of damming, triggering landslides, some of which are active until present. The lower reach of the Geren has experienced fast base level lowering and changed regime from meandering to a straight channel. Complex response to base level change is still ongoing in the Geren and Gediz catchments. These findings are summarized in a diagram conceptualizing lava damming and breaching events. This study demonstrates that one lava flow filling a valley floor can block a river at several locations, leading to different but interrelated fluvial responses of the same river system to the same lava flow.
•A young lava flow was age-constrained using novel feldspar Luminescence.•Fluvial response to two dam events by a lava flow was different, but interrelated.•A conceptual framework of damming, breaching and response is presented.•Complex fluvial response to past damming-breaching events is still on-going.
In community-acquired pneumonia (CAP), the role of biomarkers to shorten duration of antibiotic treatment has not been firmly established. We assessed the effectiveness of active feedback of ...treatment algorithms based on procalcitonin (PCT) and C-reactive protein (CRP), compared to standard care, on the duration of antibiotic treatment in patients hospitalized with community-acquired pneumonia (CAP) in non-ICU wards. We performed a randomised, open label, parallel group, multi-centre trial in 3 Dutch teaching hospitals. Treatment was guided by a PCT algorithm, CRP algorithm or standard care. Participants were recruited by a member of the study team and randomised at day 2-3 of admission in a 1:1:1 ratio. Treatment was discontinued upon predefined thresholds of biomarkers that were assessed on admission, day 4 and days 5-7 if indicated. The primary outcome was total days on antibiotic treatment until day 30. In total 468 participants were included in this study. The median days on antibiotics (IQR) was 7 (IQR 7-10) in the control group, 4 (IQR 3-7) in the CRP group (rate ratio (RR) of 0.70, 95% CI 0.61-0.82 compared to standard care; p <0.001), and 5.5 (IQR 3-9) in the PCT group (RR of 0.78, 95% CI 0.68-0.89 compared to standard care; p <0.001). New antibiotics within the first 30 days were prescribed to 24, 23 and 35 patients in standard care, CRP and PCT groups, respectively. The hazard ratio for a new prescription in patients in the PCT group compared to standard care 1.63 (CI 0.97-2.75; p = 0.06). No difference in time to clinical stability or length of stay was found. A strategy of feedback of CRP-guided and PCT-guided treatment algorithms reduced the number of days on antibiotic in the first 30 days after hospital admission in non-ICU wards for CAP. The study was not powered to determine safety of shortening duration of antibiotic treatment. (NCT01964495).
•The physical landslide model LAPSUS-LS was suitable for modelling the influence of vegetation on slope stability at the catchment scale.•The depth of the potential shear surface and root density ...were the most important parameters determining the volume of soil displaced during a landslide.•When the shear surface was 1.5 m deep, mixed coffee and tree plantations improved stability compared to coffee because of higher deep root density•When the shear surface was 1.0 m deep, no differences in stability were found between plantations as shallow rooting densities were similar.
The influence of vegetation on slope stability is well understood at the slope level but scaling up to the catchment level is still a challenge, partially because of a lack of suitable data to validate models. We tested the physical landslide model, LAPSUS_LS, which models slope stability at the catchment scale. LAPSUS_LS combines a hydrological model with a Limit Equilibrium Method model, and calculates the factor of safety of individual cells based on their hydrological and geomorphological characteristics. We tested two types of vegetation on slope stability: (i) coffee monoculture (Coffea arabica) and (ii) a mixed plantation of coffee and deep rooting Erythrina (Erythrina poeppigiana) trees. Using soil and root data from Costa Rica, we performed simulations to test the response of LAPSUS_LS to root reinforcement, soil bulk density, transmissivity, internal friction angle and depth of shear plane. Furthermore, we modified the model to include biomass surcharge effect in the calculations. Results show that LAPSUS_LS was most sensitive to changes in additional cohesion from roots. When the depth of the shear plane was fixed at 1.0m, slopes were not unstable. However, when the shear plane was fixed to 1.5m, the mixed plantation of coffee and trees stabilized slopes, but the coffee monoculture was highly unstable, because root reinforcement was low at a depth of 1.5m. Soil transmissivity had a limited impact on the results compared to bulk density and internal friction angle. Biomass surcharge did not have any significant effect on the simulations. In conclusion, LAPSUS_LS responded well to the soil and vegetation input data, and is a suitable candidate for modeling the stability of vegetated slopes at the catchment level.
In this study we propose a model to assess the location of shallow landslides and their impact on landscape development within a timeframe of years to decades. Processes that need to be incorporated ...in the model are reviewed then followed by the proposed modelling framework. The capabilities of the model are explored through an application for a forested 17 km
2 study catchment in Northern New Zealand for which digital elevation data are available with a grid resolution of 25
×
25 m. The model predicts the spatial pattern of landslide susceptibility within the simulated catchment and subsequently applies a spatial algorithm for the redistribution of failed material by effectively changing the corresponding digital elevation data after each timestep on the basis of a scenario of triggering rainfall events, relative landslide hazard and trajectories with runout criteria for failed slope material. The resulting model will form a landslide module within the dynamic landscape evolution model LAPSUS. The model forms a spatially explicit method to address the effects of shallow landslide erosion and sedimentation because digital elevation data are adapted between timesteps and on- and off-site effects over the years can be simulated in this way. By visualization of the modelling results in a GIS environment, the shifting pattern of upslope and downslope (in) stability, triggering of new landslides and the resulting slope retreat by soil material redistribution due to former mass movements can be simulated and assessed.
Physically-based, catchment scale sediment delivery models have become increasingly complex, sophisticated and are suitable for a diverse range of environmental contexts. However, in their attempts ...to best represent the physical processes of erosion and deposition, these models require large and detailed input datasets. When such data are unavailable, annual sediment yield models are relied upon. However, in this class of models, widely available data such as daily precipitation and discharge are disregarded resulting in a reduction in temporal accuracy. To fill this scientific and management gap, the landscape evolution model LAPSUS was adapted (LAPSUS-D) for a meso-scale catchment to model sediment yield on a daily resolution. The water balance component within the model enables the calibration of the model in terms of water discharge with measured daily discharge at the outlet. This methodology is especially important when modeling sediment yield from catchments which are ungaged catchments in terms of sediment, but where hydrological data are available. As the simulation of sediment yield was the main objective of the study, the calibration focused on peak discharge. The focus on peak discharge provides insight into the capability of the model to generate, route and deliver sediment at the outlet of a meso-scale catchment. LAPSUS-D has daily temporal resolution and requires a 10 to 30m pixel size DEM, soil map, land-use map and daily hydrological records (precipitation and discharge). In this paper we present the first assessment of the hydrological model performance and an analysis of the sensitivity of the model to input parameters. Our study site is a 23-km2 catchment in Upper Nysa Szalona, southwest Poland with temperate climate.
Results show that the model can reliably predict peak discharge, which is expected in future studies to allow reliable estimates of sediment transport capacity, redistribution and yield.
•First test of the hydrological functioning of a new sediment delivery model LAPSUS-D•Works on meso-scale: both spatial (20–200km2) catchments and daily time-steps•Only needs: DEM, soil map, land-use map and daily precipitation and discharge•First test in Polish catchment shows good results for peak discharge simulation.•Good hydrological prediction gives a good indication for sediment dynamics.
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