Bedload Discharge Research Articles

Multi time scale influence of dams on bedload transport

Dams are ones of the main sources of anthropogenic disturbance to the ecology and geomorphology of rivers. The aim of the present study is to understand the mechanisms underlying their influence on downstream bedload transport in three gravel-bed rivers in the Morvan massif, France. The hydrological disturbance caused by four dams is examined at a short (2.4–2.7 years) and longer (21–28 year) time scale. At the short time scale, bedload displacement was monitored (RFID) at 8 study sites around the dams. Morpho-sedimentary characterization of the bed substrate was performed at the study sites and combined with analyses of the long profile evolution and the current cross profile.The flood regime has been to a varying extent durably reduced by the dams depending on their size and purpose: the mean annual maximum flood was reduced by 9 to 40% and the number of flood events by 27 to 73.5% over the 21–28 years period. Sediment availability and loose structures were found above the dams and below medium-sized dams (<10 m) with a null or moderate influence on the flood regime (configuration I). Sediment deficit, consolidated structures, bed coarsening and vegetation encroachment were observed within 20 km downstream of large dams (>15 m) influencing strongly or moderately the flood regime (configuration II). These morpho-sedimentary features significantly affect the current bedload dynamics, creating conditions more or less favorable for the mobility of the present and incoming bedload. The cumulative mean bedload distances of RFID tracers in configuration II are significantly lower (6.8–45 m) than in configuration I (78–315 m). The current flow management of the dams has only a moderate effect on the bedload distances recorded, as shown by the mean virtual bedload velocities, which confirm the different dynamics (0.42–0.91 m/d, and 0.62–6.44 m/d, for II and I respectively). Our results demonstrate how modifications of dams on flow and bedload discharge altered the downstream morphology, but also that this inherited morphology may now be the main controlling factor of bedload transport. These findings invite further discussion about the most appropriate ways to restore rivers downstream of dams when dealing with multi-decadal inherited morphological features.

Entrainment and deposition of boulders in a gravel bed river

Abstract. Bedload transport, entrainment of coarse sediment by a river, is inherently a stochastic and intermittent process whose monitoring remains challenging. Here, we propose a new method to characterize bedload transport in the field. Using an uncrewed aerial vehicle (UAV) equipped with a high-resolution camera, we recorded yearly images of a bar of the Grande Rivière des Vieux-Habitants, a gravel bed river located on Basse-Terre Island (Guadeloupe, French West Indies). These images, combined with high-frequency measurements of the river discharge, allow us to monitor the evolution of the population of sediments of a diameter between 0.5 and 0.75 m on the riverbed. Based on this dataset, we estimate the smallest discharge that can move these boulders and calculate the duration of effective transport. We find that the transport of boulders occurs for approximately 10 h yr−1. When plotted as a function of the effective transport time, a given population of boulders decreases exponentially with an effective residence time of approximately 17 h. This exponential decay suggests that the probability of dislodging a grain from the bed is proportional to the number of grains at repose on the bed, an observation consistent with laboratory experiments. Finally, the residence time of bedload particles on a riverbed can be used to evaluate bedload discharge.

Bedload Fluxes in a Glacier‐Fed River at Multiple Temporal Scales

AbstractIn mountain rivers, long‐term observations of water and sediment fluxes are crucial for understanding the dynamics of bedload fluctuations. We analyze 7 years of continuous data gathered from eight geophone plates at a monitoring station in the glacier‐fed Sulden/Solda River (South Tyrol, Italy) to estimate the bedload flux at 1‐min scale. Sixty‐five bedload samples were used to derive the calibration equations adopted to quantify the transported bedload mass. The signal power is proposed as a more effective metric than threshold‐based impulses for calculating bedload masses. Results show (a) a remarkable variability of bedload rates for the same value of flow discharge, (b) the joint effect of storm‐driven flood events and seasonal changes in sediment supply on bedload rates, and (c) the strong impact of climatic factors (i.e., temperature and snow cover) on bedload fluxes. Moderate bedload rates occurring in late spring/early summer are likely related to the mobilization of riverbed sediments, while sustained bedload transport during melt flows in July–August—corresponding to the effective bedload discharge range—is associated with the activation of glacial and proglacial sediment sources. The data set shows a complex climatic control on bedload transport at the basin scale, where precipitation, air temperature, and snow cover determine flow and glacier melting dynamics. These findings suggest how the effects of climate change in the Alps likely will lead to an increase in peak bedload rates in a context of declining annual bedload yields as melt flows will progressively reduce in the next decades.

Catastrophic beach sand losses due to erosion from predicted future sea level rise (0.5–1.0 m), based on increasing submarine accommodation spaces in the high-wave-energy coast of the Pacific Northwest, Washington, Oregon, and Northern California, USA

The U.S. Pacific Northwest (PNW) coastline (1000 km) has been analyzed for conditions that could impact beach erosion from potential near-future (100 year) sea level rise (SLR). Heavy mineral analysis of river, beach, and shelf samples (n = 105) establish the sources of the beach deposits. River bedload discharge and intervening estuarine sinks for river sand supplies (n = 31) were normalized to the one century time interval. Twenty-six subcell beaches (657 km in combined length) were surveyed (153 profiles) for beach sand widths (20–412 m) and sand cross-sectional areas (20–1810 m2) above wave-cut platforms and/or 0 m tidal datum. Cross-sectional areas were multiplied by beach segments to yield subcell beach sand volumes (0.4 × 106 m3–35.8 × 106 m3 ± 20% uncertainty). Innermost-shelf profiles were measured for distance to the 100-year depth of closure (30 m) to digitize the areas of inner-shelf accommodation space. Both innermost-shelf and estuarine accommodation space volumes for beach sand displacements were established for 0.5 and 1.0 m SLR. The existing subcell beach sand volumes and computed new beach sand supplies (rivers and longshore transport) were subtracted from the estimated sand volumes lost to submarine accommodation spaces to establish potential beach sand deficits from near-future SLR. Of the 26 surveyed active-beaches, some 60% and 80% (by length) are predicted to be lost, respectively, from the 0.5 m and 1.0 m SLR or equivalent littoral sand sedimentation in submarine accommodation spaces. Projected losses reach 90% for all PNW beaches (~900 km total length) from 1.0 m SLR. The computed beach sand deficits are used to estimate soft-sand retreat distances or erosional beach step backs (50–590 m ± 35% uncertainty) in unrevetted barrier spit and beach/dune deflation plains from 1.0 m SLR. Such empirical accommodation space analyses should have worldwide relevance to predicting beach erosion from near-future SLR.

Sediment transport and roughness coefficients generated by flexible vegetation patches in the emergent and submerged conditions in a semiarid alluvial open-channel

In the semiarid environment, low vegetation cover and deforestation on the banks of rivers represent a strong impact on the flow resistance process, altering the interaction of the flow with the banks, one of the conditioning factors of the morphological balance of the river channel. In extreme hydrological events, turbulence and high speeds can cause a marked erosion process at the banks, increasing the sediment yield. This study aimed to monitor water and solid discharges through direct hydrosedimentometric measurements, as well as to estimate, using a simplified model based on force balance, the hydraulic roughness coefficients generated by flexible vegetation element of the Ipomoea pes-caprae species under emergent and submerged conditions. The total annual rainfall for 2019 was 748.5 mm year−1, above the historical mean (642.80 mm year−1). The mean depth (h = 0.24 m) and flow (Ql = 0.15 m3 s−1) rates were highly correlated as a power function (R2 = 0.8041). In general, without specifically considering the effect of vegetation, the flow regime was characterized as turbulent and subcritical flow (Re = 66,634.65 dim. and Fr = 0.16 dim.), respectively. The suspended sediment concentration (CSS), suspended sediment (QSS) and bedload (QBed) discharges presented mean values of 409.41 mg L−1, 6.23 t day−1 and 0.069 t day−1, respectively. The total sediment yield (Yt) was 1.90 t km−2 year−1. The vegetation effect was analyzed on the right (RB) and left (LB) banks, where the stems of I. pes-caprae were concentrated between 0.22 and 0.40 m and 0.66–1.20 m from the banks, respectively. On the RB, the shear (1.0 < Sr < 1.95), free flow (0.27 < Sr < 1.0) and the transition (Sr = 1) zones were identified. On the LB, just emergent condition (Sr < 1.0) was indetified. The following relationship were found between vegetation drag coefficient (C′D), stem Reynolds number (Red), plant density Reynolds number (Rev) and Froude number (Fr) on the RB: C′D (1.22–12.46 m−1); Red (567 < Red < 2224), Rev (1305 < Rev < 35,011) and Fr = 0.14; on the LB: C′D (2.10–1168.29 m−1); Red (57 < Red < 1427), Rev (2615 < Rev < 167,534) and Fr = 0.08. These results demonstrate that the aquatic vegetation directly influences the river dynamics; the density vegetation having a hydraulic impact on the flow transport capacity, that is, as the C′D increases, it increases the resistance of the vegetation to the flow and decreases the capacity of transport of sediments.

Evaluation of Field Application and Estimation of Bedload Discharge in the Forest Watershed using the Hydrophone

Evaluation of Field Application and Estimation of Bedload Discharge in the Forest Watershed using the Hydrophone

Estimating Bed Load Discharge Using an Acoustic Sensor for Sediment Disaster Prevention

This study examined the possibility of estimating bed load discharge using a pipe hydrophone, an acoustic measurement sensor. To that end, a small-scale on-site hydraulic experiment device was built, and regression equations were developed based on the analysis of collision sound signals by bed load discharge, grain size distribution, and flow velocity change. They were classified into pulse and sound pressure integral-based regression equations according to the characteristic value of collision sound. To verify the regression equations, the calculated values of bed load discharge were compared with the actual values. The results showed that the regression equation based on the sound pressure integral had a higher accuracy than the pulse-based regression equation, and the error rate compared to the measured value was approximately 19%. The Index of Agreement (IoA) was found 0.83, indicating a good agreement between the changing trend and estimated value of bed load discharge. It is believed that sediment disasters could be prevented by incorporating various experimental conditions and establishing a corrective relationship with the actual bed load discharge in the river.

Bed-Load Collision Sound Filtering through Separation of Pipe Hydrophone Frequency Bands

Bed-load discharge of a river can be monitored by indirectly measuring the acoustic pulses generated when the bed load collides with a steel pipe installed on the riverbed (i.e., pipe hydrophone measurement). However, existing methods used for filtering pulses from acoustic signals reflect a combination of bed-load collision frequency bands, thereby limiting characterization capabilities. This study proposes an improved filtering method that separates and efficiently examines frequency bands that are highly correlated with bed-load collision characteristics. Herein, an experimental hydraulic model and bed-load collision sound-measurement system were constructed, and bed-load collision experiments were repeatedly performed for collecting acoustic data using a pipe hydrophone. Fast Fourier Transform analysis was performed on data to select the specific frequency bands and pressures reflecting the bed-load particle size. Furthermore, a bandpass method to examine bed-load collision sounds is also presented herein. Results indicate that in comparison with existing filtering methods, the proposed bandpass method yields higher detection rates under bed-load conditions of low flow rate and small particle size, thereby demonstrating its enhanced effectiveness.

River Channel Forms in Relation to Bank Steepness: A Theoretical Investigation Using a Variational Analytical Method

Riverbanks vary considerably in anti-scourability and consequently take various profiles. By using an isosceles trapezoid as the generalized form of river channel cross-sections and then incorporating the effects of bank angle into the variational analytical approach developed by Huang and Nanson (2000), this study presents a detailed theoretical investigation of the self-adjustment of alluvial channel forms. It is demonstrated that when alluvial channel flow achieves stable equilibrium, a significant decrease in riverbank steepness leads to a slight decrease in maximum sediment (bedload) discharge, and yet results in a significant increase in optimal channel width and a considerable decrease in optimal channel depth. The hydraulic geometry relations, theoretically derived for bank steepness to vary across a wide range, show that among the multivariant controls, the roles of bed sediment size, channel roughness, flow discharge and sediment (bedload) discharge are independent of bank steepness. While the effects of bank steepness illustrated in the theoretically derived hydraulic geometry relations are highly consistent with the results of threshold theory and previous empirical studies, limitations on using bank angle to reflect the anti-scourability of natural riverbanks are also highlighted.

Sediment Characteristics of Bed Load Transport in Downstream of Progo River, Indonesia

Progo River is one of the rivers that has a sediment supply from volcanic and non-volcanic areas. Sediment transport, especially the bed load transport, it is very influential on the phenomenon of river degradation and aggradation. Therefore, a study to determine the characteristics of bed load transport is needed and important. The research was carried out in the downstream part of Progo River. Sampling locations were taking in four locations, namely Ancol Bridge, Kebon Agung II Bridge, Kebon Agung I Bridge and Bantar Bridge. The bed load transport measurement tool was used Helley Smith (WMO, 1980) equipment. Every river cross section is taken three times. The results showed that the sediment type of bed load transports is silty sand, with specific gravity values of 2.67 to 2.70. The average diameter values (D50) of the bed load transports vary greatly from 0.129 mm to 0.454 mm. The values of bed load transports vary greatly and are influenced by the values of the discharges. The correlation between bed load transport and discharge is linear, with R values are 0.85 to 0.99.

On the Effect of the Froude Number and Hydromorphometric Parameters on Sediment Transport in Rivers

A number of requirements for sediment transport formulas are considered for using in mathematical and physical models of alluvial channels. Some formulas (Bagnold, Petrov, Kopaliani) are analyzed and compared. It is demonstrated that the universal bed load transport formula should implicitly contain the Froude number. At the same time, the dependence of bed load discharge on the hydraulic resistance coefficient and the non-moving flow velocity increases the calculation error. However, these parameters, must be taken into account in simulating bed deformations for non-uniform sediments.

Bedload transport measurements in the Gilgel Abay River, Lake Tana Basin, Ethiopia

Little is known about the contribution of bedload flux to the total sediment load exported from tropical sand-bed rivers. Yet, predicting bedload transport rates contributes to better river management, more appropriate river engineering works design, accurate knowledge of sediment delivery rates, which greatly benefits sediment-related water resources management. Therefore, bedload, suspended load and runoff discharge were measured at the lower Gilgel Abay River in the Blue Nile catchment of Ethiopia. Catchment area is 3887 km2, average stream discharge in the rainy season 315 (±164) m3 s−1, and the stream surface gradient at the sampling station 0.0007 m m−1. A standard Helley-Smith (U.S. BL-84) cable-suspended sampler was used to take 315 samples to measure bedload fluxes for the 2017 rainy season. The bedload predominantly comprises well to moderately well sorted, medium-sized sand (250–500 µm) with a symmetric and leptokurtic distribution. The mean daily observed bedload discharge varies from 0.7 to 427.5 Mg d−1 with an average rate of 175.1 Mg d−1. Field observations also show that the bedload dynamics become larger near the river banks and decrease towards the middle of the river section due to the presence of a central bridge pier. The average suspended sediment load ranges from 247 to 220,028 Mg d−1 and dominates the total sediment yield (>94.6%). The bedload accounts for only 0.1 to 5.4% of the total sediment load. The area-specific bedload and suspended load are also 0.6 and 22 Mg ha−1 yr−1 respectively. The elongated planform growth of the Gilgel Abay River delta in Lake Tana is also in line with the predominance of very fine, suspended load in the sediment transport of this river, in addition to limited alongshore drifting given the low waves of Tana lake. Among the tested bedload prediction criteria, the stream-power based equations of Martin and modified Bagnold performed better. Yet, the bedload prediction performance of simple power regression equations based on runoff discharge and excess unit stream power parameters provided the best agreement with the observed bedload data (Adj. R2 0.82–0.87). Finally, this study provides plausible estimates of bedload fluxes that are within predicted ranges reported for sand-bed rivers in Africa and other tropical regions.

Study on characteristics of sediment and bed load discharge in Sungai Jemberau at Tasik Chini

This study had been carried out to identify sediment characteristics in Sungai Jemberau at Tasik Chini, and to compare their bed load dischargedata between the measured and predicted methods. It was observed that extensive uncontrolled mining activities nearby Sungai Jemberau had led to erosion and hence increasing bedload discharge. This situation hadbecome worst during storm or rainfall events because of increased sedimentation process.The river depth hadbecome shallow as the river bed was filled with bedload settles on the riverbed. Due to this situation, flooding becomes more severe as the river overflows. From here, the bedload discharge can be estimated using the DuBoys and Schoklitsch equation. Sediment size was classified using the Udden Wentworth Scale. Mostly, the median grain size (d50) wasin a range of 2.0mm to 4.0mm, and was classified as Very Fine Gravel (VFG). Meanwhile, the density of sediment was in a range of 2.34g/cm3 to 2.97g/cm3. Lastly, the comparison between the measured and predicted bedload discharge shown that DuBoys equation gives better prediction of bedload discharge in Sungai Jemberau.

The characteristics of bedload discharge monitored by sediment discharge and hydrological observation at debris flow occurrences and its application for monitoring in mountain river basin

The characteristics of bedload discharge monitored by sediment discharge and hydrological observation at debris flow occurrences and its application for monitoring in mountain river basin

Numerical method for bed load discharge estimation

This paper put forward a new method to estimate the bed load discharge through numerical model of bed load. Based on the concept of none-equilibrium bed load discharge, using numerical model and reverse problem solving approach through numerical simulation, this paper estimated the bed load transportation rate of the riverbed. A numerical model that can describe none-uniform and none equilibrium bed load transportation was developed in this paper. The model can simulate the hydraulic factors, Manning coefficient, bed load transportation rate, and the change of bed sediment graduation with the change of the time. Through the solution of the flow continuous equation, flow momentum equation, resistance equation, none-equilibrium bed load transportation equation and the sediment mass continuous equation, the deformation of the river bed is obtained. This model is applied to rivers with the following features: the gravel-cobble bed with sand, the little effect of the suspended sediment on the deformation of the river bed, the depth and width of none-uniform flow along the river. The model was verified by a set of flume experiment of none-equilibrium bed load discharge. The results indicate that the observed bed load transportation rate is consistent with the computational one. The results of the computing bed sediment gradation reflect the phenomenon that the scour and silting cause the larger of the bed sediment correctly. This model was applied to the estimation of bed load discharge of Changma Reservoir near the dam site, and estimate that the ratio of bed loads to suspended load 14%, which is very close to 16%–the estimation of the physical model experiment.

Bedload Sediment Concentration of Sungai Kahang Downstream Kahang Dam in Johor

Dams construction globally on rivers have generated a significant adjustment to stream hydrology and sediment dynamics. The impoundment of rivers by dam reservoirs will trap the sediments following freely downstream the river channel. Kahang dam is constructed to impound Sungai Kahang (Kahang River) for water supply purposes; this may have adverse effects downstream the dam by starving the river its natural sediments and changing the river flow. This study evaluates the bedload sediments and river discharge downstream the dam by taking field measurements, using the area-velocity and single increment method at three selected gauging locations (St0, St1, St2). The results obtained between January and July 2017 show the highest bedload discharge for all the gauging Stations to be 0.0736 tones/day at St0 and 0.0077 tones/day at St2 while the river flow remains relatively steady between 0.528 m3/s to 2.534 m3/s. The high bedload discharge recorded can be attributed to the anthropogenic activities going on during external construction works going on, as lower bedload concentration values followed immediately after the external construction work was completed.

Deformation and Noneroding Velocities in Channels Composed of Inequigranular Soils

The noneroding velocities in channels composed of inequigranular soils that are determined with consideration of the formation of a natural channel bed armor layer are overstated in the construction codes and regulations (SNiP-06.03.85). It is suggested to use in calculations the noneroding velocities determined with the formation of natural armoring and to calculate the depth of scouring and diameter of armor by the method proposed herein or A. V. Magomedova’s method. This article examines deformations of a model canal channel in inequigranular, noncohesive, rather coarse-grained soils with an average particle diameter greater than 0.55 mm, in which the formation of natural armor is possible at velocities insignificantly exceeding the noneroding. A calculation scheme is proposed. It is suggested to consider channel scour normal to the slopes. It is suggested to estimate the time of deformations with the use of the probabilistic formula based on K. I. Rossinksii’s model for bedload discharge. To determine the diameter of the natural armor and scour depth, a calculation method is proposed which gives values close to those obtained in experiments.

Development of new sensor systems for continuous bedload monitoring using a submerged load‐cell system (SLS)

AbstractIt is important to evaluate bedload discharge and temporal changes of the bed surface, and bed deformation can be estimated during floods if the bedload discharge is properly evaluated in an arbitrary cross‐section. With the exception of grain size and its distribution within the bedload, bedload discharge has been measured using both direct and indirect methods. Bedload slot is a direct method but cannot be used to measure bedload during a flood because of volume limitations. Indirect methods require correlation between the signals and sediment volume measured using another method. In the present study, a small, automatically recording bedload sensor with an iron plate and a pair of load cells is developed in order to evaluate not only large particles but also sand particles as bedload. Bedload mass is calculated by integrating with respect to both the velocity of sediment particles and the averaged particle weight as measured by a pair of load cells, and, as an example, the velocity is estimated by the cross‐correlation function of weights measured by load cells. The applicability of the proposed sensor is discussed based on the results of flume tests in the laboratory (2014) and the observation flume of the Hodaka Sedimentation Observatory of Kyoto University in Japan (2015). The system was installed in the observation flume in November of 2012, and flume data were obtained using natural sediment particles. In particular, it was difficult to estimate the velocity of averaged bedload particles, and it was better to apply a cross‐correlation function in the laboratory tests. However, it appears that the previous estimation can estimate these velocities in the observation flume using a connecting tube and submerged load‐cell systems. Copyright © 2017 John Wiley &amp; Sons, Ltd.

Transport measurement with a horizontal and a vertical pipe microphone in a mountain stream: taking account of particle saltation

AbstractThe pipe microphone has been shown to be an effective means for monitoring bedload transport in mountain streams. It is commonly installed perpendicular to the flow direction on a stable river bed, such as that of a check dam. Acoustic pulses caused by bedload collisions with the pipe are detected by a microphone. However, bedload particles saltating over the pipe remain undetected. To overcome this disadvantage, we installed a horizontal as well as a vertical pipe microphone in the Ashi‐arai‐dani supercritical channel located in the Hodaka mountain range, Japan. The vertical pipe was installed on the wall of the channel and the horizontal pipe was installed on the channel bed. The acoustic response of the horizontal pipe is expected to be larger than that of the vertical pipe, because the bedload concentration decreases with increasing height above the bed. However, at high amplifications, the peak pulse value from the vertical pipe is higher than that from the horizontal pipe. We explain this observation as follows: under high bedload discharge conditions, the pulses of the horizontal pipe are saturated but those of the vertical pipe are not. We proposed a ratio (Rhv) between the pulses detected by these sensors, and applied this ratio for calibrating the contemporaneous pulses detected by a microphone located immediately upstream of a bedload slot sampler. Indeed the Rhv‐corrected pulses correlated well with the bedload discharge calculated from the sampler, supporting our explanation. We conclude that bedload monitoring using concomitant vertical and horizontal pipe microphones can be used to calibrate centrally located pipe microphones when the bedload concentration is approximately homogeneous laterally across the width of the channel cross‐section, and thereby represent bedload discharges more accurately than with only a single pipe microphone. Copyright © 2017 John Wiley &amp; Sons, Ltd.

An estimate of bedload discharge in rivers with passive acoustic measurements: Towards a generalized calibration curve?

Bedload Self-Generated Noise (SGN) measurements consist in deploying an underwater microphone (i.e. a hydrophone) in the river and to record the ambient noise. The use of hydrophones to measure bedload characteristics (flux, spatial distribution, granulometry) could be of interest as it can be more easily and rapidly deployed than physical samplers in rivers. Several measurement campaigns where conducted during spring and summer 2017 in 5 alpine rivers with contrasted transport conditions (bedload D50 between 1 and 40 mm) and varying slopes (0.05 to 1 %). Physical sampling measurements were done from a bridge along the river cross section for specific bedload flux varying between 10 and 150 g.m-1s-1. Bedload SGN measurements were obtained with a small board equipped with a hydrophone and deriving downstream the bridge within a 10 to 50 m long river section. For 2 of the 5 rivers, acoustic Doppler current profilers (ADCP) were also deployed along the river cross-section to provide a surrogate measurement of apparent bedload velocity. As a result, we have been able to draw an acoustic 1D-map of the river bottom, derived from the SGN sub-surface measurements obtained with the deriving board. The results show a coherent relation between the riverbed acoustic maps and the physical samplings for 3 rivers over 5. Bedload profile were less consistent with SGN measurements when bedload transport was localized in a narrow channel. The apparent bedload velocities obtained with ADCP for 2 rivers are consitent with the physical samplings (bedload location and flux distribution) but a slight bias was observed and is attributed to grain-size sorting effects along the cross-section. Finally, when plotting together 4 over 5 rivers, an almost linear relation can be established between bedload discharge (computed with physical samplings data) and the average acoustic response (i.e acoustic power averaged over the cross-section). This result suggests that a generalized calibration curve could exist between bedload SGN and bedload discharge. The existence of an outsider is interpreted as a problem related to propagation effects. Further researches should therefore concentrate their effort on deconvoluting SGN signals from propagation effects to give a better confident proxy for bedload discharge measurement in different rivers types.