16Bedload transport assessment is important for geomorphological, engineering, and 17 ecological studies of gravel-bed rivers. Bedload can be monitored at experimental 18 stations that require expensive maintenance, or using portable traps, which allows

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Suspended sediment transport can affect water quality and aquatic ecosystems, and its quantification is of the 13 highest importance for river and watershed management. Suspended sediment concentration (SSC) and dis-14 charge were measured at two locations in the Estero Morales, a Chilean Andean stream draining a small basin 15 (27 km 2 ) hosting glacierized areas of about 1.8 km 2 . Approximately half of the suspended sediment yield 16 (470 t year −1 km −2 ) was transported during the snowmelt period and half during glacier melting. The hysteresis 17 patterns between discharge and SSC were calculated for each daily hydrograph and were analysed to shed light 18 on the location and activity of different sediment sources at the basin scale. During snowmelt, an unlimited sup-19 ply of fine sediments is provided in the lower and middle part of the basin and hysteresis patterns tend to be 20 clockwise as the peaks in SSC precede the peak of discharge in daily hydrographs. Instead, during glacier melting 21 the source of fine sediments is the proglacial area, producing counterclockwise hysteresis. It is suggested that the 22 analysis of hysteretic patterns over time provides a simple concept for interpreting variability of location and ac-23 tivity of sediment sources at the basin scale.24

Coarse bed load transport is a crucial process in river morphodynamics but is difficult to monitor in mountain streams. Here we present a new sediment transport data set obtained from 2 years of field-based monitoring (2014)(2015) at the Estero Morales, a high-gradient stream in the central Chilean Andes. This stream features step-pool bed geometry and a glacier-fed hydrologic regime characterized by abrupt daily fluctuations in discharge. Bed load was monitored directly using Bunte samplers and by surveying the mobility of passive integrated transponder (PIT) tags. We used the competence method to quantify the effective slope, which is the fraction of the topographical slope responsible for bed load transport. This accounts for only 10% of the topographical slope, confirming that most of the energy is dissipated on macroroughness elements. We used the displacement lengths of PIT tags to analyze displacement lengths and virtual velocity of a wide range of tracer sizes (38-415 mm). Bed load transport in the Estero Morales shown to be size-selective, and the distance between steps influences the displacement lengths of PIT tags. Displacement lengths were also used to derive the statistics of flight distances and resting times. Our results show that the average length of flight scales inversely to grain size. This contradicts Einstein's conjecture about the linear relationship between grain size and intervals between resting periods in a steep step-pool stream in ordinary flood conditions.

Suspended and bedload transport dynamics on rivers draining glacierized basins depend on complex processes of runoff generation together with the degree of sediment connectivity and coupling at the basin scale. This paper presents a recent dataset of sediment transport in the Estero Morales, a 27 km2 glacier-fed basin in Chile where suspended sediment concentration (SSC) and bedload (BL) fluxes have been continuously monitored during two ablation seasons (2014–2015 and 2015–1016). The relationship between discharge and SSC depends on the origin of runoff, which is higher during glacier melting, although the hysteresis index reveals that sediment sources are closer to the outlet during snowmelt. As for suspended sediment transport, bedload availability and yield depend on the origin of runoff. Bedload yield and bedload transport efficiency are higher during the glacier melting period in the first ablations season due to a high coupling to the proglacial area after the snowmelt period. Instead, on the second ablation seasons the peak of bedload yield and bedload transport efficiency occur in the snowmelt period, due to a better coupling of the lower part of the basin caused by a longer permanency of snow. Differences in volumes of transported sediments between the two seasons reveal contrasting mechanisms in the coupling dynamic of the sediment cascade, due to progressive changes of type and location of the main sources of runoff and sediments in this glacierized basin. The paper highlights the importance of studying these trends, as with retreating glaciers basins are likely producing less sediments after the “peak flow”, with long-term consequences on the ecology and geomorphology of rivers downstream.

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<p>Geomorphic changes in rivers often happen after either single high magnitude floods or several following ordinary flood events. Erosion and deposition have been well documented in all types of rivers, as well as the formation and destruction of step-pool sequences. However, there are less evidence available on the link between erosion-deposition at the reach scale and the formation-destruction of geomorphic units. This work is based on a series of field surveys carried out in a small glacierized basin in the central Chilean Andes. The location and extent of erosion/deposition were quantified using the photogrammetric technique with a drone before and after a high magnitude flood occurred during autumn 2016. High-resolution Digital Elevation Models (DEMs) were computed to generate erosion-deposition maps (DoD; Difference of DEMs). Also, orthomosaics were used to derive maps of geomorphic units for a 100-m long study reach, before and after the studied flood event. Results show an overall deposition of sediments in the study reach, but a decrease in the number of step-pool sequences from 20 to 14. Step-pool destruction is linked to depositional patterns, whereas the formation of new step-pool sequences is more likely to occur in erosional zones. Rapids and cascades also change in number, increasing from 1 to 4 units, and their formation was related to the deposition of sediments. These results may have larger implications in terms of ecological habitat dynamics and are also important for planning and management in civil projects like bridges and hydropower water intakes</p>

<p>Coarse bed load transport is a crucial process in river morphodynamics, but it is difficult to monitor in mountain streams. Predicting bed load is a difficult task especially in steep step-pool streams, where the critical dimensionless shear stress is affected by local channel slope and relative submergence, and only part of the flow energy is available to entrain and transport sediments as some is dissipated in local hydraulic plunging and jumps. Here we present a new sediment transport dataset obtained from two years of field-based monitoring (2014-2015) at the Estero Morales, a high-gradient stream in the central Chilean Andes. This stream features step-pool bed geometry and a glacier-fed hydrologic regime characterized by abrupt daily fluctuations in discharge. Bed load was monitored directly using Bunte samplers and by surveying the mobility of passive integrated transponder (PIT) tags. We used the competence method to quantify the effective slope, which is the fraction of the total slope responsible for bed load transport. This accounts for only 10% of the total slope, confirming that most of the energy is dissipated on macroroughness that characterize step-pool stream. We used the displacement lengths of PIT tags to derive the statistics of flight and resting times, observing that the average length of a flight scales inversely with grain size.</p>