Siltation

About: Siltation is a research topic. Over the lifetime, 1420 publications have been published within this topic receiving 20983 citations.

Sediment suspension and the dynamic mechanism during storms in the Yellow River Delta

Abstract: The suspension and hydrodynamic characteristics of the Yellow River Delta during storms were analyzed based on suspended samples obtained using automatic samplers during a storm event in the Yellow River Delta. Synchronous data for winds, waves, and tides were also collected from a nearby station. The results show that under wind speeds of 5–15 m/s and wave heights of 50–150 cm, the suspended content reached 5.7–49.6 kg/m3, which is 10–100 times higher than that under normal weather conditions. The medium diameter of suspended particles was 1.2–2.1 μm (8.9–9.7 Φ), which was approximately 1–2 Φ finer than that under normal weather conditions. During the early stages of the measurements, the sea level had risen by 50 cm owing to the storm, which was in addition to the tidal sea level change. We suggest that during the storms, the waves strengthened and the storm-induced sea level change, which was combined with tidal currents moving in the same direction, produced high-speed currents. This overcame the cohesive forces among the fine sediment particles and suspended a large amount of sediment. As a result, the suspended content increased markedly and the suspended particle size became finer. This explains the intense siltation and erosion of the Yellow River Delta during storms.

Transportation and Adjustment of Different Grain Sized Sediment Along the Lower Yellow River under Typical Operation Modes of Sanmenxia Reservoir

Abstract: The degradation and aggradation of the Lower Yellow River are affected by the operation modes of the Sanmenxia Reservoir. Under the influences of clear water or water of low sediment concentration released from the reservoir, the channel of the Lower Yellow River was eroded and the sediment concentration was recovered, but the concentration of fine sediment recovered slowly in a long distance, while the coarse and medium sediment recovered fast in a rather short distance. When the reservoir was flushed, the Lower Yellow River was serious silted because of the low discharge, high sediment concentration and coarse sediment sluiced from the reservoir. The quantity of siltation accounted for 60%～70% of the incoming sediment load, in non\|flood season, the channel of the Lower Yellow River was eroded by clear water from the reservoir. The eroded sediment from the channel bed was relatively coarse in the reach upstream of Huayuankou. The eroded coarse and medium sediment accounted for 30%～40% respectively with the median size of 0 04mm. The erosive distance was increased with the increasing of discharge. After the Spring flood, the capabilities of sediment transport for different sized sediment were decreased because of the armouring of the composition of the channel bed, and the quantities of eroded sediment were also decreased correspondingly. When the reservoir was flushed in pre\|flood season, the grain size of flushed sediment was 0.005～ 0.042mm. The deposition mainly occurred in the reach upstream of Huayuankou. The quantities of deposition for different sized sediment were determined by the incoming sediment and were not related to the incoming discharge. The grain size also was a significant factor affecting the quantities of deposition.

A study of sediment characteristics and riverbed erosion/deposition in Qiantang estuary

Abstract: In this paper,the distribution characteristics of sediment concentration and sediment grain size are introduced in brief,and the formulas of the sediment incipient velocity and the sediment carrying capacity in the estuary are establishedThe characteristics of the large variation amplitude of the riverbed,the rapid deposition after rapid erosion,the flood-induced eroding and the tide-induced silting in the upper reach,and the flood-induced silting and the tide-induced eroding in the lower reach are analyzedThe riverbed variation has a great impact on flood and tidesWhen tidal bore arrives,the flows of the tidal bore violently erode riverbed and result in sharply increased sediment concentration,which mostly reaches a peak value after twenty minutes,thus forming a high sediment concentration regionIn normal and dry periods,sediment discharge in flood tide is larger than that in ebb tide,resulting in silting in the upper reachThe tidal bore is one of the mechanisms for serious erosion and deposition of riverbed in the Qiantang estuary

Siltation disturbance in a mountain stream: aspect of functional composition of the benthic community

Abstract: Background and Purpose: Siltation is a recognized stress for the benthic community. It may cause changes in the structure of habitat substrate and water physical and chemical properties. The aim of this study was to ascertain the effects of siltation on the function of a mountain stream benthic community, specifically in respect to availability of food resources. Materials and Methods: The study was carried out at Bistra Stream on the Medvednica Mountain in NW Croatia. Siltation was caused by quarrying. Samples were taken at a control (unsilted) site and three impact sites on four dates during the spring of 2006. Turbidity, water temperature, pH, oxygen content, conductivity and COD were measured and triplicate benthos samples were taken using a 30 ́30 cm Surber sampler on each sampling date. Impact of siltation on functional feeding guilds was analyzed. Results and Conclusions: Turbidity, pH and temperature increased significantly downstream of the siltation source. Total number of individuals decreased by 85%, number of taxa by 60% and Shannon’s diversity index followed accordingly (by 56%). The grazers and the detritivores were proven to be most sensitive to the disturbance. The disturbance did not strongly affect shredders whereas predator abundance increased. We conclude that change in food availability is a crucial aspect of siltation disturbance and that allogenic siltation is more devastating because of the additional chemical changes not noted during natural siltation.

A long-term numerical model of morphodynamic evolution and its application to the Modaomen Estuary

Abstract: Because of the influence of human activities, the evolution of the Modaomen Estuary is no longer a purely natural process. We used a long-term morphodynamic model (PRD-LTMM-10) to study the evolution of the estuary from 1977 to 1988. The model incorporated modules for riprap-siltation promotion and waterway dredging. The model can simulate the morphodynamic evolutionary processes occurring in the Modaomen Estuary during the period of interest. We were able to isolate the long-term influences of various human engineering activities and the roles of natural factors in estuarine evolution. The governance projects had the largest effect on the natural development of the estuary, resulting in larger siltation on the west side. Installation of riprap and reclamation of submerged land resulted in scouring of the main Hengzhou Channel causing deep trough out-shift. Severe siltation narrowed the upper end of the Longshiku Deep Trough.