Suspended Load Discharge Research Articles

Assessment of Annual Erosion and Sediment Yield Using Empirical Methods and Validating with Field Measurements—A Case Study

To implement soil conservation approaches, it is necessary to estimate the amount of annual sediment production from a watershed. The purpose of this study was to determine the erosion intensity and sedimentation rate from a watershed by employing empirical models, including the modified Pacific Southwest Inter-Agency Committee (MPSIAC), the erosion potential method (EPM), and Fournier. Moreover, the accuracy of these empirical models was studied based on field measurements. Field measurements were conducted along two reaches of Babolroud River. Total sediment transport, including suspended load and bed load, was predicted. Bed load transport rate was measured using a Helly–Smith sampler, and suspended load discharge was calculated by a sediment rating curve. The results of this study indicate that the erosion intensity coefficient (Z) of the Babolroud watershed is 0.54, with a deposition rate of 166.469 m3/(km2.year). Due to the existence of unusable crops, the highest amount of erosion appeared in the northern region of the watershed. The results using the EPM and MPSIAC models were compared with field measurements and indicated that both models provided good accuracy, with differences of 22.42% and 20.5% from the field results, respectively. Additionally, it could be concluded that the Fournier method is not an efficient method since it is unable to consider the erosion potential.

Distribution Characteristics of Phosphorus in the Yarlung Zangbo River Basin

Phosphorus is an important limiting biogenic material. The special topography and climate of the Yarlung Zangbo River Basin generate unique distribution and transport characteristics of total phosphorus (TP). A survey of TP concentration, precipitation, runoff, sediment content, suspended load discharge, and relevant data was carried out for the Yarlung Zangbo River Basin in the last ten years. In combination with the regional geography and social economies, the basic spatial-temporal characteristics of P-water-sediment were analyzed by using the correlation and time series analysis methods. Furthermore, the transport characteristics of P and the main control factors were also studied. The results show that the TP concentration in this basin displays the characteristics of interannual cyclical variation and annual phasic variation, and the peak value appears in the wet season. Among the Yarlung Zangbo River, Nyangqu River, Lhasa River, and Nyang River, the TP concentration is the highest in the Nyangqu River, exceeding 0.4 mg/L several times in the wet season. In this basin, the distribution patterns of the TP concentration are similar to those of the rainfall, runoff, suspended load discharge, and sediment concentration. The coupling property of the TP concentration is the strongest with the suspended load discharge among the meteorological and hydrological parameters. The spatial variation of dissolved P in the wet and dry seasons in 2016 responded to the distribution patterns of the population density, environmental factors, farming, and animal husbandry. This indicates that the TP in the water is mainly from non-point sources and is affected by agricultural, geographical, and ecological factors. The transport of TP is mainly controlled by the suspended load discharge due to precipitation.

Discrete-Time Markov Chain Model for Transport of Mixed-Size Sediment Particles under Unsteady Flow Conditions

AbstractA nonhomogeneous discrete-time three-state Markov chain model is developed in this study to quantify the bedload and suspended load discharge under unsteady flow for mixed size sediment particles. When flow is subject to sudden changes, the particle holding time, defined as the amount of time for a sediment particle staying on the bed or in the moving state, needs to be carefully evaluated. The time step used in this study for single-step motion in the discrete-time Markov chain is represented by a characteristic timescale for particle motion. The transition probabilities are functions of flow conditions and particle properties. Specifically, the likelihood of particle movement between the bedload layer and the bed surface is evaluated by the entrainment probability. Exchange of sediment particles between the bedload layer and suspended load layer is quantified by the suspension probability. A nonhomogeneous Markov chain ensures the transition probabilities are time dependent as they are a functio...

Present versus long term sediment yield to the Adriatic Sea and the reliability of gauging stations data

The current denudation rate over an 128 000 km2 catchment area, encompassing the southern watershed of the Alps, the eastern watershed of the Northern Apennine and part of the Dinarides, was evaluated by means of a wide-reaching appraisal of the suspended load discharge of rivers now feeding the Northern Adriatic Sea. Data from gauging stations located on Alpine and Northern Apenninic rivers were matched to data derived from reservoirs silting and delta growths in lacustrine basins. The area weighed denudation rate obtained from suspension and solution load measurements in the southern watershed of the Alps is 0,071 mm/a while for the Northern Apennine it amounts to 0,431 mm/a. Reservoir silting surveys indicate values of respectively 0,151 and 0,771 mm/a, which also include the bed load component of river sediment yield. The difference is however also due to traditional point sampling techniques frequently underrating the suspended yield of rivers. The Alpine values are consistent with those reported by [Hinderer (1999][1], [2001)][2] which are based on different data sets. The present denudation rates are then compared with literature data on long term average denudation rates (post LGM, Quaternary, Pliocene). The present-day impact of man as a geological agent is not clearly evidenced by modern rates when compared to long term ones, since the manifold indirect and direct anthropic influences largely balance each other. [1]: #ref-17 [2]: #ref-18

7200 years of Rhône river flooding activity in Lake Le Bourget, France: a high-resolution sediment record of NW Alps hydrology

Magnetic susceptibility (MS) was measured with high resolution (5 mm) on a 9 m long, 14C dated core from Lake Le Bourget (Savoie, France), spanning the last 7200 years. The strong correlation (R=0.85) of the MS with the silicate-borne suite of elements (Si, Al, Fe, Mg, K) and anti-correlation with the carbonate content (R =-0.87) allows it to be used as a proxy for the fluctuations of the abundance of riverborne clastic fraction versus authigenic carbonates in sediment. As the Rhône is the only river bringing a significant amount of silicate minerals to the coring site, the MS downstream is interpreted as a proxy of the Rhône suspended load discharge in Lake Le Bourget. This is confirmed over the last 3000 years by the good match with the evolution of hydrological activity of the Rhône as it is known through geomorphological studies of well-dated archaeological sites. Over the last 7200 years, the record is consistent with the regional record of lake water-level fluctuations. While the intensity of the MS signal might be widely affected by the human impact on soil stability, the timing of the period of enhanced hydrological activity appears to be mostly climate-related, and should thus constitute a first step toward a high-resolution (< 8 yr) continuous history of hydrological conditions in the NW Alps.

Extreme events controlling erosion and sediment transport in a semi‐arid sub‐andean valley

AbstractThe importance of extreme events in controlling erosion and sediment transport in semi‐arid areas has long been appreciated but in practice being by definition rare and episodic they are difficult to study. When they are observed this is frequently in catchments for which little data are available. Another difficulty is that even when catchments are being monitored the instruments that record discharge, sediment load and hillslope sediment fluxes perform inaccurately or unpredictably during extreme weather conditions. This paper describes slope and channel processes that were actually observed by the authors during a (at least) 1 : 30 year 30 minute event with a rainfall intensity of 240 mm h−1 in a second‐order tributary of the Rio Camacho near Tarija in southern Bolivia. During the event, it could be observed how different tributary streams and slope sections contributed sediments and flow to the main channel. Evidence for these contributions did not survive the event, which has implications for both modelling and monitoring. Before the onset of the event open erosion plots were functioning on the slopes where rainfall and runoff were being measured. Rainfall experiments were used to obtain infiltration rates.The storm began with a moderate intensity of about 5 cm per hour but increased after 5 minutes to 30 cm per hour and continued for 30 minutes. At this time, the rainfall intensity greatly exceeded the infiltration capacity and water started draining the steep slopes. The ephemeral channel rapidly filled up with runoff. Erosion by hailstones was considerable.Provisionally, the discharge during peak runoff was estimated at 43·7 m3 s−1 (Manning equation). On the basis of sediment loads carried by previous storms, (average concentration of 21 g l−1) the total suspended load discharge during the storm would have been 15 ton ha−1. Within the ephemeral channel, 10 to 50 cm thick layers of coarse sediments were deposited. The collectors of the open erosion plots could not handle the large amounts of runoff and sediment and were completely filled to overflowing.Comparing these data with soil losses during less intense storms it can be concluded that extreme events largely contribute to erosion and sediment transport and that the majority of the rainstorms play only a minor role. The results also show how limited the values of rainfall experiments are in understanding geomorphic events. This makes modelling of erosion and soil losses a difficult and hazardous task. Copyright © 2002 John Wiley & Sons, Ltd.

Estimation of siltation of the Tereblya-Rika hydroelectric station reservoir

An estimation of the suspended-load discharge with the use of the existing data of hydrological yearbooks was not very reliable, since it gave quite underestimated results of the calculation in comparison with the actual volumes of siltation of the reservoir.

Mississippi River Shoaling: A Diagnostic Study

The field study was conducted to collect definitive data on the flow and sediment movement characteristics in the recurrent shoaling reaches of the Mississippi River in the vicinities of Fox Island (RM 355-6) and Buzzard Island (RM 349-50) in Pool 20 between Keokuk, Iowa and Canton, Mo. The detailed field data were used to identify the source of the excess sediment input into the Mississippi River, and to elucidate the principal mechanisms of shoaling processes in the study areas by establishing empirical relationships of the bed-load discharge and the suspended-load discharge with the mean flow velocity and the water discharge.

Untersuchungen über Zusammensetzung und Transport von Schwebstoffen in einigen Schweizer Flüssen

Abstract. The amount and composition of suspended load from 19 stations in Swiss rivers werestudied. Generally, the correlation between the amount of suspended load and of water discharge is good, although measurements over short periods of time show large fluctuations. The denudation rate was calculated from the suspended load discharge, the amount of elements in Solution, and the water discharge. Values of about 0.05 mm/yr were obtained for drainage areas consisting mainly of crystalline rocks and about 0.25 mm/yr for drainage areas dominated by sedimentary rocks. The mineralogical composition of the suspended load determined by X-ray diffraction can be correlated with the rock types in the drainage areas. Composition changes resulting from transportation were not observed. The clay fraction is mainly composed of illite and chlorite which was, for the most part, formed during mechanical weathering in the Alps.

SEDIMENT TRANSPORT IN THE RIVULETS NEAR KAIFUURA, NIIGATA PREFECTURE

In a former paper the writer (TAKAYAMA, S. 1956) mainly treated the problem of bed load transport. The present article describes the results of measurement on the transportation of suspended load of sediment by the three rivulets. In Fig. 1 are presented writer's results of measurement of the suspended load on these rivers (Hayakawa, Fukogawa and Okawa). Both the appreciable scatter of the points and the limited coverage of discharge range are evident. However, the trends of the regression lines indicate that suspended load discharge increases continuously with increasing discharge. The equations for the lines for average conditions of Hayakawa, Fukogawa and Okawa are respectively: Ha akawa; QS=114.1 Q2•48 Fukogawa; QS=89.9 Q1•72 Okawa; QS=51.3 Q2•06in which Qs is the suspended load in tons per second, Q is the water discharge in cubic meter per second. The coefficient and the exponent in the equations are different from each other due to the condition of the surface of the drainage area at the time, the rate of availability of sediments and other factors. Usually the suspended load seems to vary approximately as the square roots of the water discharge and this means that the values of increment of suspended load with water discharge is generally larger than that of bed load. Two fairly distinct trends could be discerned (one for the flood occured August through September when high flows take place; the other for the flood of October when flood stage is not so high) from Fig. 1. This difference is thought to be due to the changing volume of fine-grained river bed material which can be easily transported. That is, the river bed is filled with fine-grained particles subsequent to several weeks of low stages; then the flood peak in August and September completely removes these particles. Total sediment discharge is computed as the sum of suspended discharge and bed load discharge. It is the total quantity of sediment as measured by dry weight, that is discharged during a given time. For example, in Fig. 2, the area under the curves (QS-T and QB-T) represent the sum of suspended load [QS] and that of bed load [QB] respectively during a flood (Tab. 1) . Hydrograh for this flood is shown in Fig. 3. The percentage ratio of [QB] to [QS] (hereafter designated as QB/QS) varies with the scale of flooding as shown in Fig. 3. There is a tendency that the bed load movement dwindles to small portions as the maximum water discharge increases. The gross amounts of sediment transported as bed load, suspended load and total sediment load during the observed period are calculated by continuous summation of [QB], [QS] and [QT] of each flood and Σ QB, Σ QS and Σ QT obtained as tabulated in Tab. 2. In order to provide data on comparative basis, these values are reduced to the values per square kilometer of drainage area. There are great spatial variations among them and these differences may be reflected not only in the character of sediment but also in the landforms themselves in each drainage area. The geomorphic features which appear to be significant to sediment delivery are mean altitude of a drainage basin, maximum relief in a drainage area, mean watershed slope, mean channel slope and mean relief ratio (Fig. 4 & 5, Tab. 3).