Seasonal Sediment Transport Research Articles

Using Field Measurements Across Land Cover Types to Evaluate Albedo‐Based Wind Friction Velocity and Estimate Sediment Transport

AbstractThe soil surface wind friction velocity (us*) is an essential parameter for predicting sediment transport on rough surfaces. However, this parameter is difficult and time‐consuming to obtain over large areas due to its spatiotemporal heterogeneity. The albedo‐based approach calibrates normalized shadow retrieved from any source of albedo data with laboratory measurements of aerodynamic properties. This enables direct and cross‐scale us* retrieval but has not been evaluated against field measurements for different cover types. We evaluated the approach's performance using wind friction velocity (u*) measurements from ultrasonic anemometers. We retrieved coincident field pyranometer and satellite albedo at 48 sites that were spread over approximately 1,800 km on the Inner Mongolia Plateau, including grassland, artificial shrubland, open shrubland, and gobi land. For all cover types, u* estimates from ultrasonic anemometers were close to the albedo‐based results approach. Our results confirm and extend the findings that the approach works across scales from lab to field measurements and permits large‐area assessments using satellite albedo. We compared the seasonal sediment transport across the region calculated from albedo‐based us* with results from an exemplar traditional transport model (QT) driven by u* with aerodynamic roughness length varying with land cover type and fixed over time. The traditional model could not account for spatiotemporal variation in roughness elements and considerably over‐estimated sediment transport, particularly in partially vegetated and gravel‐covered central and western parts of the Inner Mongolia Plateau. The albedo‐based sediment transport (QA) estimates will enable dynamic monitoring of the interaction between wind and surface roughness to support Earth System models.

The Role of Seasonal Sediment Transport and Sintering in Shaping Titan's Landscapes: A Hypothesis.

Titan is a sedimentary world, with lakes, rivers, canyons, fans, dissected plateaux, and sand dunes. Sediments on Saturn's moon are thought to largely consist of mechanically weak organic grains, prone to rapid abrasion into dust. Yet, Titan's equatorial dunes have likely been active for 10s–100s kyr. Sustaining Titan's dunes over geologic timescales requires a mechanism that produces sand‐sized particles at equatorial latitudes. We explore the hypothesis that a combination of abrasion, when grains are transported by winds or methane rivers, and sintering, when they are at rest, could produce sand grains that maintain an equilibrium size. Our model demonstrates that seasonal sediment transport may produce sand under Titan's surface conditions and could explain the latitudinal zonation of Titan's landscapes. Our findings support the hypothesis of global, source‐to‐sink sedimentary pathways on Titan, driven by seasons, and mediated by episodic abrasion and sintering of organic sand by rivers and winds.

Using Drone and LiDAR to Assess Coastal Erosion and Shoreline Change due to the Construction of Coastal Structures

Tak, W.J.; Jun, K.W., Kin, S.D., and Lee, H.J., 2020. Using drone and LiDAR to assess coastal erosion and shoreline change due to the construction of coastal structures. In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 674-678. Coconut Creek (Florida), ISSN 0749-0208.Recently, The construction of structures on the coastal zone near estuaries, which are the supply sources of sediments, causes a variation in the waterway; this induces a change in the surrounding coasts, and the resulting coastal erosion can adversely affect the lives of the local residents. In the case of a balanced sediment flow, the quantity of the sediment deposited on the coast is equal to the quantity of the released sediment. However, an increase in either of the quantities causes an imbalance in the sediment transport; consequently, the sand is either deposited or eroded in the coastal or proximate shore regions. In this study, the changes in the shoreline and Wolcheon Beach region located on the east coast of Korea was monitored between 2010 to 2019 investigate the phenomena of coastal erosion and beach deformation. The shorelines, beach width, and beach profile were primarily monitored by employing a drone and a terrestrial LiDAR. The results showed that the sediments were transported northward in summer and southward in winter until 2010 in Wolcheon Beach; however, this seasonal sediment transport was blocked during 2011–2012 by the construction of coastal structures such as breakwaters, leading to partial coastal erosion and sedimentation. Wolcheon Beach originally had the coastal characteristics of the Korean East Coast region (2010), but the sediment transport changed due to the variations in the waterway by the construction of coastal structures, leading to a significant change in the coast (2011). In addition, the northern beach volume increased with respect to estuary, while the southern beach volume decreased. When the offshore breakwater was constructed, the northward sediment occurred dominantly in the shield area. In particular, the planar layout of the harbor facilities concentrated the waves, which increased the quantity of the northward sediment.

Impacts of Hydro-Climatically Varying Years on Ice Growth and Decay in a Subarctic River

Predicting the future changes in river ice development and impacts on seasonal sediment transport requires more in-depth examination of present river ice cover growth processes. This paper therefore investigates: (1) the impacts of hydro-climatically varying years on river ice development in a Scandinavian subarctic meandering river and (2) the accuracy of existing analytical models for predicting ice thickness growth and ice decay. Stefan’s ice growth equation (version by Michel et al.) and Bilello’s ice decay equation are applied to varying hydro-climatic conditions experienced in the years 2013–2019. Estimates from these equations are compared with observed field conditions such as ice thicknesses, ice clearance dates and freeze-thaw days. Overall, the equations were most accurate in the winter of 2016–2017 when the maximum mid-winter snow thickness value was high, the number of freeze-thaw days was the closest to the long-term average of northern Scandinavia, and the rate of thermal snow-melt in the subsequent spring was slow. The equations would need to be adjusted to take into account expected future changes to conditions such as shorter winters, less snow formation and increased frequency of air temperatures crossing 0 °C.

Sensitivity assessment of the deltaic coast of Medjerda based on fine-grained sediment dynamics, Gulf of Tunis, Western Mediterranean

As coastal areas become increasingly vulnerable to climate change, the study of nearshore sediment textures along the littoral cell of the Medjerda delta in the Gulf of Tunis, southern Mediterranean coast can provide valuable information (i) on the origin (continental or marine) of the sediment, (ii) its transport direction, and (iii) constitutes an important tool in the assessment of coastal sensitivity. A total of 120 sediments samples underwent grain size analysis and statistic parameters have been calculated. These allowed the identification of five different Sedimentary Types (ST). Accordingly, using grain size indexes (i.e. Mz, SKI and Ku), Sediment Trend Analysis (STA) modeling tools were applied to define the seasonal sediment transport pathways throughout the nearshore of the Medjerda sedimentary cell. Results show that grain size distribution (GSD) and STA model pathways are determined by cross-shore geomorphology, location of the sediment-cell, seasonal incident wave and local terrestrial supply. The appearance in an atypical seabed location of the finer (Mo = 0.1 mm) and the coarser STs (Mo = 0.8 mm) can be indicative of human influence since the coarser particles are usually retained by dam structures. Moreover, the bimodality and the increased distribution of mud are also related to the seasonal incident wave winnowing of the historic deltaic plain submerged by the relative rise in sea level. The evolution of the sediment pattern towards a greater proportion of very fine grains indicates a deficit of sediment supply, particularly of the coarser grains, and demonstrates the coastal vulnerability of the Gulf of Tunis due to anthropic effects.

Sediment Bypassing from the New Human-Induced Lobe to the Ancient Lobe of the Turbo Delta (Gulf of Urabá, Southern Caribbean Sea)

Alcantara-Carrio, J.; Caicedo, A.; Hernandez, J.C.; Jaramillo-Velez, A., and Manzolli, R.P., 2019. Sediment bypassing from the new human-induced lobe to the ancient lobe of the Turbo Delta (Gulf of Uraba, Southern Caribbean Sea). Journal of Coastal Research, 35(1), 196–209. Coconut Creek (Florida), ISSN 0749-0208.Artificial river diversions cause intense and unpredictable changes in the geomorphological evolution and sedimentary dynamics of deltas. This study analyzes the effects of the 1958 course diversion of the Turbo River delta, Gulf of Uraba, southern Caribbean Sea. Recent satellite images were analyzed and beach topography was monitored to obtain the shoreline migration and sediment budget; surface sediments were seasonally sampled, and their grain size parameters were determined; and seasonal sediment transport directions were deduced according to grain size trends. It was concluded that the bimodal wave regime controls the seasonal sedimentary patterns associated with southward longshore transport during both the dry and rainy seasons, and the northward longshore transport occurs in the midsummer drought. Beach morphodynamics of Yarumal Point, close to the present-day river mouth, show that this is the most exposed sector to waves, whereas fluvial sediment inputs are evidenced by a decrease in mean grain size and by poorly sorted sediments in the rainy season. A new spit is forming in Yarumal Point, with an intense increase in area and a westward progradation related to high fluvial sediment inputs from the La Nina event of 2010–12 and low erosion from the El Nino events of 2009–10 and 2015–16. In the central sector, longshore drift has formed the Yarumal barrier spit with a southeastward progradation that recently closed the interdistributary El Uno Bay. Consequently, a humaninduced sand barrier–lagoon system resulted with a stable or slightly regressive shoreline. Moreover, the Yarumal barrier spit has generated a new sediment bypass to Barajas Beach in the northern limit of the Las Vacas spit (i.e. the ancient delta lobe). Therefore, there is an unusual accretion of the abandoned delta lobe by sediment supply from the new lobe.

Climate change impacts on bedload transport in alpine drainage basins with hydropower exploitation

AbstractSediment transport is known to have a significant impact on hydropower infrastructures and changes in sediment transport rates are important for sediment management measures and hydroelectricity production. In this study, we present how climate change may affect bedload transport in 66 high alpine catchments used by hydropower companies in the Valais, Switzerland. Future sediment yield is estimated with a runoff‐based sediment transport model for the two future 30 year time periods 2021–2050 and 2070–2099. The analysis is integrated into a modelling chain in which error‐corrected and downscaled climate scenarios generated in the framework of the ENSEMBLES project are coupled to the hydrological model PREVAH, glacier retreat and bedload transport. To calibrate the sediment transport model, we used the observed sediment volumes in water intakes and reservoirs if such data were available. The results obtained show on average a decrease of sediment yield due to the reduced runoff generation during summer, especially for the scenario period 2070–2099. A shift of the seasonal sediment transport regime with a current maximum during July and August to earlier months in the year is predicted. Projections of future sediment yield rely on the accuracy of the individual modeling chain elements. The different sources of uncertainty are discussed qualitatively. Copyright © 2015 John Wiley & Sons, Ltd.

Simulation of Seasonal Bathymetric Change at Haeundae Beach with Two Representative Wave Settings

Kim, H.; Jin, J.Y.; Jang, C.; Yoo, H.J., and Hwang, D.H., 2014. Simulation of seasonal bathymetric change at Haeundae Beach with two representative wave settings.Long-term shoreline position of Haeundae Beach has been quite stable notwithstanding seasonal oscillatory movement. Bathymetry around Haeundae Beach was surveyed on 7 August 2007 and 12 November 2007 by using an echo-sounder, while wave, tide, and tidal current were measured between the two survey days, so that bathymetric change at Haeundae Beach was obtained from the two surveys. According to the surveys the east part of the beach was eroded, and the west part of the beach was accreted. Measured waves from SSE, SE, ESE, E during the period were stronger than measured waves from S, SSW, SW, WSW. A numerical model system CST3D was adopted to reproduce the bathymetric change at Haeundae Beach during the period. Two representative wave settings are chosen for the period as a minimum number to represent the time-series of wave record, based on equivalent sediment flux concept contained in the CERC formula. Wave field, wave-induced force field, wave-induced current field, sediment transport field, and bathymetric change are computed from individual modules, SWAN, WIF, FLOW, SED in CST3D, respectively. Computed bathymetric change agrees reasonably well with measured one. It is believed that selection of two representative wave settings is useful for simulation of seasonal bathymetric change for fairly straight morphology like Haeundae. CST3D is thought to effectively describe overall seasonal sediment transport pattern and consequent bathymetric change at Haeundae Beach.

Temporal variations of suspended sediment transport in Oneida Creek watershed, central New York

► The exponent of a sediment rating curve reflects the degree of sediment supply. ► Short-term sediment variations can be averaged out at longer time scales. ► A process-based approach for seasonal sediment loads and sediment yields. Using event-based suspended sediment data collected from 2008 to 2010 in a medium-size agricultural watershed in Central New York, we first examined the statistical properties of suspended sediment concentration, C and the associated water discharge, Q . Next, we identified two different transport processes in two discharge ranges separated by a different threshold Q t for each season. Different exponents of sediment rating curves (SRCs) in each season revealed that sediment was transported near capacity during lower discharges but well below capacity during higher discharges. The persistence of these two trends in all seasons suggested that suspended sediment transport was generally supply limited. Sediment loads predicted by a single seasonal SRC are similar to those predicted by the two separate SRCs for above and below Q t , which suggests that the two transport processes are not significantly different and seasonal sediment transport may be described by a single SRC. The better fit of SRC for the combined 3-year data compared to those for individual years indicates that seasonal changes of suspended sediment transport are limited and the transport dynamics that emerge at shorter time scales (i.e., event and season) are effectively averaged out. We then calculated sediment yields for 3 years using a process-based SRC method: annual hydrograph was divided into storm and base flows using values of Q t for all seasons and only storm flows were used to calculate sediment yields based on the developed SRCs. Comparing sediment yields of 3 years calculated using three seasonal SRCs to those using the combined 3-year SRC indicated that the discrepancies between the two were less than 5%, suggesting that sediment yield may be accurately estimated using the single combined-year SRC. Finally, we discussed the appropriate sampling strategy in the region and demonstrated geomorphological nature of sediment transport based on the calculated effective discharges and cumulative sediment loads.

An Extreme Sediment Transfer Event in a Canadian High Arctic Stream

Two large suspended sediment concentration (SSC) pulses were recorded in 1998 in a small snowmelt-fed stream on Ellesmere Island in the Canadian High Arctic. The largest pulse occurred from 7 to 8 July, when 32% of the monitored seasonal sediment transport occurred in only four hours. SSC reached 83,760 mg L−1, exceeding all previously recorded values from high arctic glacially-fed and snowmelt-fed rivers by more than one order of magnitude. The event occurred after the majority of snow in the watershed had melted, and was preceded by a long period of relatively high air temperature, and a small rainfall event on 7 July. We consider the most likely cause of the event to be a rapid mass movement.

Seasonal sediment transport pathways in Lirquen Harbor, Chile, as inferred from grain-size trends

Bottom sediment samples were collected in June and December 1997 at 166 stations on a rectangular grid in a small port (Lirquen Harbor, BioBio Region, Central Southern Chile) facing siltation problems with a view to determining local seasonal sediment transport pathways through the application of three different methodologies based on grain-size trends. Measured winds and near-bottom currents together with hindcast wave allowed to establishing the influence of the prevailing meteorological and hydrodynamic conditions on local sediment circulation. The results suggest that transport of deep and shallow water sediments occur rarely under high-energy conditions. The current data suggest that tidal asymmetry would be an important agent of sediment transport in Lirquen Harbor. The sediment transport pathways inferred from grain-size trends are compared with the measured water circulation of the study area and sediment dispersal patterns on aerial photographs. The results yielded by the grain-size trend methodologies of Gao-Collins (1992) and Le Roux (1994b) indicate a possible seasonal variation in transport pathways agreeing with the prevailing meteo-hydrodynamic conditions, whereas the McLaren-Bowles (1985) approach does not show a significant difference. It is suggested that the latter methodology may represent transport on a spatial macroscale as opposed to the mesoscale patterns yielded by the other two techniques. Based on the results of the three grain-size trend methodologies, the observed current and wind data, the hindcast wave data and aerial photographs a conceptual model of net annual sediment transport is proposed for Lirquen Harbour.

Seasonal sediment transport and deposition in the Rajang River delta, Sarawak, East Malaysia

The Holocene Rajang River delta plain, which covers an area of 6500 km 2 , has developed in a tropical, ever-wet climatic setting. Peat deposits, up to 15 m thick, occur in this delta plain. The tributary system to the delta is about 50,000 km 2 in area. Elevations exceed 2000 m in the drainage basin and hill slopes are steep. Rainfall in the region exceeds 370 cm/year, with highest rainfall levels or the “wet” season being coincident with the December‐March monsoon. The monthly drainage-basin discharge is calculated to average about 3600 m 3 /s, and the discharge normally ranges from 1000 to 6000 m 3 /s. Spring tides in coastal areas range from 2.9 to 5.8 m. Tide data indicate that the tides are semidiurnal with a noticeable diurnal inequality. Vibracores recovered from bar forms in tidally influenced distributary channels contain laminated silts and sand-silt couplets that show evidence of rhythmic heterolithic stratification. Grain-size data indicate that these preserved delta plain siliciclastic sediments are the result of estuarine depositional processes that occur during intervals of reduced rainfall or the “dry” season (April‐November). The number of laminae preserved per neap‐spring cycle is the highest (o18‐20), and the average thickness is the greatest in the middle part of the delta plain. Distributary channels in this region normally contain low-salinity brackish water to freshwater. Vibracores recovered from delta front and prodelta sediments show evidence of heterolithic stratification, but rhythmicity is absent. Grain-size data indicate that preserved delta front and prodelta sediments are implaced by “wet” season processes (December‐March) when fluvial flux and delta-plain erosion are at their maxima. Individual silt laminae and/or silt and sand interbeds are sometimes many centimeters thick, but average about 1 cm. These silt laminae and silt and sand interbeds or varves represent annual sedimentation events. These varves demonstrate that about 24 million MT of sediment produced by the drainage basin is deposited in the delta front and prodelta region annually. q 2000 Elsevier Science B.V. All rights reserved.

Stochastic model for the long‐term transport of stored sediment in a river channel

We develop a stochastic model for the transport of stored sediment down a river channel. The model is based on probabilities of transition of particles among four different sediment storage reservoirs, called active (often mobilized), semiactive, inactive, and stable (hardly ever mobilized). The probabilities are derived from computed sediment residence times. Two aspects of sediment storage are investigated: flushing times of sediment out of a storage reservoir and changes in the quantity of sediment stored in different reservoirs due to seasonal sediment transport into, and out of, a reach. We apply the model to Redwood Creek, a gravel bed river in northern California. Although the Redwood Creek data set is incomplete, the application serves as an example of the sorts of analyses that can be done with the method. The application also provides insights into the sediment storage process. Sediment flushing times are highly dependent on the degree of interaction of the stable reservoir with the more mobile sediment reservoirs. The most infrequent and highest intensity storm events, which mobilize the stable reservoir, are responsible for the long‐term shifts in sediment storage. Turnover times of channel sediment in all but the stable reservoir are on the order of 750 years, suggesting this is all the time needed for thorough interchange between these sediment compartments and cycling of most sediment particles from the initial reservoir to the ocean. Finally, the Markov model has adequately characterized sediment storage changes in Redwood Creek for 1947–1982, especially for the active reservoir. The model replicates field observation of the passage of a slug of sediment through the active reservoir of the middle reach of Redwood Creek in the 18 years following a major storm in 1964 that introduced large quantities of landslide debris to the channel.