Showing papers on "Siltation published in 2004"

Physical Impacts of Marine Aggregate Dredging on Seabed Resources in Coastal Deposits

Abstract: A detailed study of the seabed surrounding dredge pits created during the mining of marine aggregate from a small licence off the south coast of the United Kingdom (“Licence Area 122/3”) has been completed. Over 350 km of high-resolution sidescan sonar imagery and 177 sediment samples have been obtained over a study area extending 10 km either side of the dredge zone (representing one full tidal excursion) in order to identify far-field effects on both physical and biological resources of the seabed. The physical results presented here for Area 122/3 clearly show that the physical impact of dredging (without screening) on the seabed is limited to a zone within approximately 300 m downtide of the dredge area. This will generally be within the dredge licence boundary due to operational procedures. There is no evidence of suspended sediments falling to the seabed beyond this zone and causing significant changes, which may be manifested as infilling of small pits by fine sediments, siltation within c...

Research Note: An approach to integrated assessement of reservoir siltation: the Joaquín Costa reservoir as a case study

Abstract: . In 1932, the Esera river was dammed at the foothills of the Pyrenean External Ranges; since then, sedimentation has reduced its water storage capacity by a third. This study of the sediments in the Joaquin Costa reservoir has been based on detailed sedimentological examination and other analysis of mineralogy, grain size distribution and the chemical components of the materials accumulated at the bottom of the reservoir. Interpretations are based on results from four sediment cores collected at sites representative of the main environments in the reservoir. Records of known flood events and of reservoir management data have been combined with a 137Cs-derived chronology. Thus, it has been possible to ascribe the sedimentary record at the different reservoir environments to specific years, as well as some main changes in the facies types and sediment components. This methodology is a first approach to assessing siltation processes and dynamics in Mediterranean mountain reservoirs. Keywords: reservoir siltation, mineralogy, sedimentology,sedimentation rates, 137Cs, sediment tracing, mountain reservoir, central Spanish Pyrenees

Using a bank erosion hazard index (behi) to estimate annual sediment loads from streambank erosion in the west fork white river watershed

Abstract: The Arkansas Department of Environmental Quality (ADEQ), through an EPA Section 319 NPS grant, utilized a bank erosion hazard index (BEHI) and data collected from surveys of streambank profile measurements to develop a graphical model to estimate streambank erosion rates and to estimate the annual sediment load due to accelerated streambank erosion in the West Fork White River (WFWR) watershed The WFWR watershed, located in Northwest Arkansas, has a watershed area of 31,700 Ha (79,400 ac) and is a tributary to the White River which eventually drains to the primary drinking water source for the region, Beaver Lake Sediment is a contaminant of concern because the WFWR has been designated as impaired due to “excessive turbidity and siltation” (ADPC&E, 1998) As part of a comprehensive project to assess the various sources of sediment in the WFWR watershed, ADEQ utilized methods, developed by Rosgen (2001), to estimate sediment (bedload and suspended) contributions from accelerated streambank erosion A streambank erosion inventory was conducted in 2002 to determine the bank erosion potential of streambanks along 64 river kilometers (40 river miles) of the main stem and tributaries of the WFWR watershed Using ranking criteria consisting of bank angle, root depth, bank material, and other variables, streambanks were evaluated and scores were assigned based on erosion potential Toe pins were installed at permanent survey sites and lateral erosion was measured over a one-year period A graphical model to predict streambank erosion rates based on relationships between BEHI, near-bank sheer stress, and observed annual erosion was developed For the WFWR watershed, it was estimated that on an annual basis, a total of 21,455 metric tons of sediment enter the river network from streambanks where accelerated streambank erosion was observed The mass of bedload and suspended load was 7,493 metric ton/yr and 13,962 metric ton/yr, respectively

Geoinformation in gully erosion studies in taita hills, se-kenya, preliminary results

Abstract: Gully erosion is a serious form of water erosion damaging agricultural areas and constructed sites such as bridges and roads, and causing siltation of rivers and reservoirs. Gully erosion has been studied in Taita Hills applying airborne digital camera orthomosaics and GIS for small-scale studies, and field measurements for large-scale studies. The objectives are 1) detection of distribution and intensity of gully erosion within Taita Hills and its changes during the last 50 years, 2) determination of the main factors affecting gully erosion and 3) development of methodologies for gully erosion hazard assessments both at large and small scales.

A simple technique using wooden stakes to estimate vertical patterns of interstitial oxygenation in the beds of rivers

Abstract: Silt and fine sediments from anthropogenic activities frequently clog river bed sediments, impairing vertical exchanges between stream and subsurface water. River managers need a simple technique to detect the extent of interstitial clogging and monitor the effectiveness of measures to reduce siltation. We evaluated the use of 30-cm long pine-wood stakes, inserted for 3-6 weeks in the sediments of four French rivers varying in interstitial clogging, to determine the association between changes in the colour of the wood and the adjacent interstitial conditions. There was a general association between depth to interstitial hypoxia and location of the colour change of the wooden stakes from brown to pale grey or black after 3-4 weeks. This change in colour also broadly matched interstitial contents of fine sediment, ammonium, and nitrate although the method could not reliably detect microscale zones of anoxia or short-term changes in dissolved oxygen. Thus, its effectiveness lies in its use as a cheap, simple, and broad-scale indicator for collecting long-term integrated data of interstitial oxygenation in stream sediments with minimal disruption of the gravel bed, and appears an ideal tool for river managers and salmonid fish biologists.

Sedimentation in small dams. Development of a catchment characterisation and sediment yield prediction procedure

Abstract: The British Government's Department for International Development commissioned HR Wallingford to develop guidelines presenting appropriate methods for predicting, and where possible reducing, siltation rates in small communal dams in semi-arid zones in Eastern and Southern Africa. Small dam designers must be able to use these methods; they typically need to carry out assessments rapidly using limited local data, and may not have software skills or access to computers. The report describes the development of a method for predicting small dam catchment sediment yields. The objective was to develop a simple procedure which would distinguish between dams that will silt up rapidly from dams that will have a sedimentation lifetime well in excess of twenty years.

The effect of freshwater flow on siltation in the Humber Estuary, north east UK

Abstract: This paper investigates the impact of variations in freshwater discharge from the Rivers Trent and Ouse on a number of factors related to siltation in the Humber Estuary. These factors include suspended sediment concentrations, bed sediment composition, bed levels and channel mobility. Seasonal increases in freshwater discharge can reduce siltation rates and lower bed levels in both the Inner and Outer parts of the estuary. Such seasonal variations in freshwater flow also lead to the downstream displacement of sandy bed sediments as well as the turbidity maximum. More extreme flood events can lead to discrete shifts in the channel configuration within the Inner Estuary. It is suggested that in the Humber there are critical values of freshwater discharge, with the exceedance of upper threshold conditions leading to reductions in bed levels and the switching of channel positions, and the reduction of flows below lower threshold conditions leading to pronounced increases in sedimentation.

Siltation and hydrologic regime determine species composition in herbaceous floodplain communities

Abstract: Interest in the restoration of riparian habitat is increasing. However, little is known about factors responsible for riparian communities, especially grasslands. In order to construct plant communities for a restoration project in the floodplain of a large river in the Midwestern United States, we sampled four floodplains with various disturbance regimes located in Illinois and Missouri. They were chosen to be representative of different plant communities of floodplains, with a focus on herbaceous communities. The areas included backwater lakes, alluvial fans, groundwater seep marshes, oxbow marshes, seasonally inundated grassland, and non-inundated grassland. Vegetation, soils and groundwater or standing water depth were measured at various intervals along transects. Communities were produced using TWINSPAN and tested for differences in environmental factors. The soil morphology, taxonomic classification, and fertility parameters were similar among sites. Environmental factors influencing community composition were the presence of permanent water and silt deposition. We conclude that water depth determines species composition in permanently wet areas. Silt deposition determines composition in seasonally inundated grassland. Where silt deposition is high enough to inhibit seedling emergence, dominance is attained by plants able to reproduce vegetatively by rhizomes. Such a reproductive process leads to nearly monotypic stands produced by large clones. Results are discussed in relation to models of riparian processes and succession.

Guidelines for predicting and minimising sedimentation in small dams

Abstract: Many of the small dams constructed in semi-arid regions of Africa rapidly fill with sediments, sometimes after only a few years. When dams silt up the rural communities that rely on them for cattle watering or small-scale irrigation are deprived of the water and food security that dams provide, and their livelihoods are seriously affected. Predicting soil erosion, sediment yields and dam sedimentation rates can be a complex task, requiring specialist expertise, and is generally poorly covered in small dam design manuals. This results in many small dams being constructed with little or no consideration of the impact of future siltation of a dam's life or on water yields. These guidelines were prepared to enable dams where siltation rates will be unacceptably large to be identified at the planning or design stage of small dam projects. Where siltation rates are expected to be large measures have to be taken to reduce sedimentation. Approximate methods for estimating the impact of remedial measures, such as catchment conservation or engineering interventions, on dam lives and water yields are also described. The methods were selected, or in some cases specifically developed, for use in typical small dam design studies. In such studies there is usually neither the site specific data nor the time and resources needed to carry out the more detailed studies that precede the construction of larger and more expensive dams.

Distribution of certain ecological parameters and foraminiferal distribution in the depositional environment of Palk Strait, east coast of India

Abstract: Out of 102 species, only 36 species are living ones. The total distribution of foraminifera is higher at Devipattinam and Attankarai followed by Mandapam, Thondi and Kodiyakkarai whereas at Kottaipattinam, Manalmelkudi and Sethubavachattiram it is noticed to be in the lower order. Organic matter and living species show positive relation. The lack of relationship between dead species and the organic matter has suggested that the dead species recorded in the sediments must have been primarily drifted/transported as empty calcareous shells. From the sand/silt/clay ratios, it is inferred that the sediments are normally sandy in nature but silty sand dominates at deeper depths. Carbonate content establishes a weak negative correlation with all parameters except organic matter and dead species. Fluctuation of salinity values in Attankarai indicates the influx of fresh water from Vaigai river. Based upon the ecological parameters the stations have been grouped into different environments. Among them, bar environment registers low species diversity than the other three. The following species are appreciably distributed in different stations namely Ammonia beccarii, Elphidium crispum, Rosalina globularis, Asterorotalia trispinosa, Osangularia venusta and Pararotalia nipponica. This strait is influenced by an unique environment of high order of siltation leading to the depletion of living forams. The present study highlights the abundance of living species in places of high organic matter. The ongoing process of active siltation is manifested in the bar environment and the same is reflected in the low organic matter and less species diversity.

Wave characteristics in Lake Taihu

Abstract: Eutrophication results not only from inflowing pollutants but also released nutrients from sediment resuspension which is caused by stress jointly induced by the combination of wave and current, and the stress caused by wave is much larger than that caused by bottom current in shallow lake. Wave can lead to shore erosion resulting in siltation in waterway, and nutrients transportation resulting in regional variation of nutrient concentrations, which can account for seasonality and regionality for algae bloom in Lake Taihu. Wave data is analyzed and wave stress is calculated. Based on the verified wind-wave model, wave stresses in summer and winter are also computed. The results show sediment resuspension can easily occur in the northwest area of Lake Taihu in summer with prevailing SE wind and in the southeast in winter with prevailing NW wind.

Assessment of hydraulic restoration of San Pablo Marsh, California.

Abstract: Inter-tidal marshes are dynamic diverse ecosystems at the transition zone between terrestrial and ocean environments. Geomorphologically, inter-tidal salt marshes are vegetated landforms at elevations slightly greater than mean tidal levels that have distributed channels formed under ebb (drainage) tidal flows that widen and deepen in the seaward direction. The drainage channels enable tidal flows to circulate sediments and nutrients through the marsh system during normal tidal events, while depositing sediments during storm or seismic events. This dynamic system encourages considerable biodiversity while simultaneously providing water quality enhancement features that service marsh terrestrial life and marine life in the estuary. Reservoir creation limiting sediment transport, anticipated large increases in sea levels as well as agricultural and urban development have resulted in significant loss of inter-tidal marshes and subsequent adverse impacts on waterfowl, infauna and fisheries. The complex and continuously changing marsh channel hydraulics and sedimentary processes have severely constrained quantitative modeling of these marsh systems such that restoration/creation efforts remain something of an empirical science and further assessments are needed.The purpose of this paper is to outline current understanding of salt marsh hydrodynamics, sediment accretion processes and subsequent response of marsh vegetation to set the stage for assessment of a marsh restoration effort along San Pablo Bay near San Francisco, California. Several kilometers of drainage channels were constructed in a 624 ha disturbed salt marsh to restore tidal circulation and vegetation so as to enhance habitat for threatened species (e.g. clapper rail, harvest mouse, delta smelt and potentially anadromous fish species). Two distinct drainage channel systems (`east' and `west') were installed having similar channel dimensions common to salt marshes in the region, but having design bankfull tidal prism volumes differing by a factor of two. Following channel excavation, main channel tidal flows and sediment loads as well as marsh sediment accretion rates were monitored to assess the relative success of the excavation in restoring tidal circulation and vegetation (Salicornia spp.) to the marsh. Annual aerial surveys corroborated with ground-truthing indicated that marsh vegetation rapidly expanded, from 40 to 85% coverage several years following excavation. The `east' channel intake was nearly completely silted in within three years. However, channel surveys and flow measurements indicated that the `east' channel system tidal prism was only about 1200 m3, more than an order of magnitude less than that of the stable `west' channel system. Marsh sediment accretion rates were on the order of 7–8 mm yr-1, a rate common to the Pacific coast region that exceeds estimated sea level rise ratesof ∼2 mm yr-1. East channel network siltation resulted in storm and spring tidal flood ponding such that marsh vegetation coverage decreased to 51% of the marsh area and related habitat expansion decreased. These results are considered in terms of the primary inter-tidal marsh factors affecting possible restoration/creation strategies.

Numerical simulation of the tidal motion and suspended sediment transport in the radial sandbank area of the southern yellow sea

Abstract: A coupled 2-D numerical model for hydrodynamic-sediment transport was established and applied to simulate the tides, tidal currents and sediment movement in the submarine Radial Sandbank area of the southern Yellow Sea. With a high-resolution topography dataset used in the model, the simulation reproduced a fine-structured current field and erosion-siltation distribution. The modeled results show that, in the area of Radial Sandbanks, reversing tidal current and seabed erosion occurs within troughs while tidal current with more rotary feature and deposition occurs above sandbanks, which indicates the tidal-induced formation of the Radial Sandbanks. During a tidal period, associating with the variation of current speed, erosion alternates with siltation. The seabed deformation depends on the relative strength of erosion and siltation in a tidal period.

Depositional environment and silting in the Sharavati estuary, central west coast of India

Abstract: Variation in textural characters (silt sand ratio, mean size, sorting and skeweness) of the Sharavati estuarine sediments has been studied to understand their depositional environment. Seventeen locations within the estuary and two locations just at the entrance of the sea were selected for the study. During September 2000, medium grained (1.36-1.86φ), well sorted to moderately well sorted sediments were observed in the estuary, whereas they were fine grained (2.67-3.φ) and poorly sorted in the entrance of the sea (0.84). The estuarine sediments were relatively fine-grained during December 2000 (postmonsoon) (1.3-2.18φ) and February 2001(premonsoon) (1.15-2.3φ) as compared to the monsoon season. The siltation in the estuary is mainly due to offshore source brought by tidal currents followed by mixing of saline and fresh water in the estuary.

The Third Test of Water and Sediment Regulation Conducted on the Yellow River

Abstract: The third test of water and sediment regulation of the Yellow River is conducted in the period from June 19 to July 13, 2004. The test has created artificial density current in the Xiaolangdi Reservoir area, regulated the sedimentation behavior which is unfavorable to the tail reach of the reservoir, increased sediment discharging capacity and decreased siltation of the reservoir through utilizing the reservoir storage before flood season, fully having the aid of natural power and reservoirs joint operation of Wanjiazhai, Sanmenxia and Xiaolangdi located on the main stream of the Yellow River and assisting with the measures of artificial sediment disturbance. At the same time, it has conducted sediment disturbance at "the secondary suspended river" of the lower reaches and the natural channel-control section where sedimentation is the most serious, reducing sedimentation in the lower channel and increased the flood capability of the main channel in the lower river by utilizing the surplus capability of sediment carrying of the water flowing into the lower channel. It has achieved the expected effects as follows: 132.9 million m~3 sediment deposited in the Xiaolangdi Reservoir area has been washed out and all 38.5 million m~3 sediment deposited above longitudinal profile of designed sedimentation balance washed away, rationally regulating the sedimentation behavior of the tail reach of the reservoir; 1.641 3 million m~3 sediment at the natural channel-control section of the downstream disturbed and 510～640 m~3/s bankfull discharge at the disturbed section increased and; each section above Lijin on the lower reaches scoured and all together 64.22 million tons of sediment in Xiaolangdi-Lijin reach washed out.

Conclusions: Scaling Relative Responses of Terrestrial Aquatic Systems to Global Changes

Abstract: From an even cursory reading of the material presented in Part D, it should be quite apparent that terrestrial aquatic Systems encompass a broad set of biogeophysical landscape features and complex processes Terrestrial aquatic Systems include water, waterborne material, sediment and biota in Vegetation, the soil unsaturated zone, groundwaters, wetlands, rivers, lakes and artificial water bodies such as reservoirs and canals The fundamental drivers of water circulation and related material fluxes (for nutrients, carbon, particulate matter, pollutants) are multiple and combine physical, chemical and biological processes including open water evaporation, precipitation, infiltration, water runoff generation, water routing, erosion, leaching, weathering, silting, evapotranspiration, biological uptake and bacterial degradation Together with their associated coastal zones, terrestrial aquatic Systems constitute what we define as Continental aquatic Systems (CAS) (Fig D94)

Changes in the Salt River, tributary to the Knysna Estuary, South Africa : 1936-1998

Abstract: Rapid changes in the lower Salt River, a tributary to the Knysna estuary, southern Cape, is documented through the use of an air photo time series. The evidence plotted for the flood plain and estuary, over the period 1936-1998, demonstrates rapid changes in the channel course, the loss of an extensive Phragmites australisl/Ig bed and siltation of the estuary. Land use changes in two western catchments particularly impacted on the hydrology. The validity of local oral evidence is confirmed. The floods in 1996 exacerbated siltation by impacting on a development in the upper Simola catchment. Sedimentation in the estuary was greater than previously recorded. The presence of coversand on interfluves and valley heads renders the entire catchment, an area of landscape sensitivity, susceptible to rapid change.

The influences of the tectonic subsidence and the siltation on the situation of preventing flood disasters in the Dongting Lake area

Abstract: With the long-term data of the geodetic sea level measurements undertaken in the Dongting Basin and the recent sediment data of Dongting Lake, we analyze the tectonic subsidence rate of the Dongting Basin and the sedimentary rate of Dongting Lake. From the point of view of geomorphology and hydrogeology, we distinguish the two different spatial concepts between “the basin of Dongting Lake” and “the Dongting Basin”. Then, we discuss the influences of the tectonic subsidence and the siltation on the levees and the space of storing flood. The better quality of levees is required due to the tectonic subsidence and the siltation, and the difficulties of preventing flood disasters are increasing. The space of storing flood is not affected by the tectonic subsidence, but by the siltation. At present, the sedimentary rate of Dongting Lake is higher than the tectonic subsidence rate of the Dongting Basin. The tectonic subsidence capacity of the Dongting Basin counteracts a part of sedimentary capacity, and the shrinking tendency of Dongting Lake is restrained to a certain extent, but the tectonic subsidence is harmful to the situation of preventing flood disasters in the Dongting Lake area.

Discussion on the evolutionary trend of Lake Dongting

Abstract: The evolution of Lake Dongting is determined by three main factors, which are tectonic subsidence, siltation and human impacts. "The Dongting Basin" and "the basin of Lake Dongting" are two different spatial concepts. "The basin of Lake Dongting" is only one of the components of "the Dongting Basin". The basin of Lake Dongting, the levees and the farmlands synchronously keep subsiding and relatively actionless due to the tectonic subsidence of the whole Dongting Basin. At present, the mean sedimentation rate of Lake East Dongting,Lake South Dongting and Lake Muping is 9.43, 19.11, 12.46mm/a, respectively. The rate of tectonic subsidence of the lake is low (3～10mm/a), but the capacity of tectonic subsidence still counteract a certain capacity of siltation, which restrains the shrinkage of Lake Dongting. The sedimentation rate is bigger than the rate of tectonic subsidence in Lake Dongting. Sandbars will continue to grow and expand, and Lake Dongting will still keep the trend of siltation and shrinkage. At present, the whole Dongting Basin is subsiding and expanding due to tectonic subsidence, which has no influence on the change of the capacity of storing flood of Lake Dongting, and siltation is playing a main role. The capacity of storing flood of Lake Dongting will continue to decrease as siltation goes on. During the 80 years after the Three Gorge Dam is completed with the completion of "the 4350 Project", the sedimentation rate of Lake Dongting will reduce to 1.79 mm/a. Then, the trend of siltation of Lake Dongting will be restrained.

Analysis of Sudden Siltation of Outer Channel of Huanghua Harbor

Abstract: Based on the study of beach patterns,wave,tidal carrent,concentration,sediment characteristic and sediment movement of the waters of Huanghua Harbor,the causes and characteristics of strong siltation and sudden siltation since the dredging of the outer channel of huanghua Harbor is analyzed.

Sedimentation in small dams. Hydrology and drawdown computations

Abstract: The British Government's Department for International Development commissioned HR Wallingford to carry out a study to develop guidelines presenting appropriate methods for predicting, and where possible reducing, siltation rates in small communal dams in semi-arid zones in Eastern and Southern Africa. Typical small dam designers must be able to use these methods; they usually have access to only limited local data, need to carry out assessments rapidly, or may not have software skills or computers. The report describes procedures used in the guidelines to carry out the hydrological computations needed to support the design of small dams and to predict future siltation.

Managing Forests for Water Quality: Forest Roads

Abstract: Water quality in forested areas can be impacted by many of these activities, including logging, fi res, other construction, recreation, and grazing. However, poorly located, constructed or maintained forest roads are the largest source of non-point source pollution on forested lands. The greatest potential for degrading water quality comes from roads on steep slopes or erodible soils, and stream crossings. Research has shown that 90 percent of the sediment that ends up in our nation’s waters from forested lands is associated with improperly designed and maintained roads. Sediment in streams leads to a number of problems for fi sh populations including siltation of spawning beds and aquatic insect habitat, increased water temperature and reduced oxygen.

Calculation of the amount of siltation and erosion in the South and North channel in the Changjiang estuary and its evolution

Abstract: The digital elevation model of the South and North channel in the Changjiang estuany is established through analyzing lots of Charts of Changjiang estuany from 1842 to 1997 by using the Kriging gridding method and the transfer relations among different datum planesThen,the relation between its channel-fill volume and the evolution of its bifurcation was analyzedThe evolution process of the South and North Channel was summarized

Evolution characteristics of the shoals of the second and third generation alluvial islands in the Changjiang Estuary

Abstract: Supported by GIS, 7 pieces of charts of the Changjiang Estuary from 1879 to 2000 are digitized and Digital elevation model (DEM) of the Changjiang Estuary in different periods is established with Kringing gridding method. Based on that the area, volume, the amount and thickness of erosion_accretion and bathymetric contour progradation rate are calculated. The results show that the trend of the shoals of the second and third generation alluvial islands in the Changjiang Estuary in the recent 150 years is that deposition as a whole and progradation seaward along southeast with deposition rates faster than that of previous time, but deposition rates in different terms were different and erosion occurred in a few terms. About 1.948 Gt of sediment was deposited between 1879 and 2000, with average annual deposition rate of 16.1 Mt, which amounts to 3.72% of sediment from the Changjiang River, and average annual thickness of 0.83cm respectively. Hengsha east beach and Jiuduansha are the main positions of siltation, while the shoals of Changxing Island and Hengshaqiantan are the main positions of erosion. As an important chain of the evolution of the Changjiang Estuary, the natural evolution of the shoals is controlled by the sediment supply from the Changjiang basin. With the increasing intensity of development in the basin and more and more projects constructed in the estuary, the impacts of human activities on the shoals in the study area is becoming more and more intense, the natural evolution of the shoals may reverse.

Study on critical conditions of scour-and-siltation in flood seasons in the lower Yellow River

Abstract: The channel bed of the lower Yellow River changes tremendously during flood seasons because of great sediment concentration.Critical conditions between scour and siltation are distinct in different river reaches.The authors summarized previous researches on the critical conditions for the lower Yellow River,analyzed statistically the hydrological data of 422 flood events from 1960 to 1999 and set up critical equations for 4 river reaches(Huayuankou upward,Huayuankou to Gaocun,Gaocun to Aishan and Aishan to Lijin) under different combinations of flow and sediment at 3 stations (Sanmenxia, Heishiguan and Xiaodong).The critical relations between flow discharges and sediment concentration for the 4 reaches were depicted.These relations may be used in the regulation of Xiaolangdi Reservoir in order to mitigate siltation for the lower Yellow River.-

Sedimentation in small dams. Estimating the impact of catchment conservation, check dams and sediment bypassing in reducing dam siltation rates

Abstract: The British Government's Department for International Development commissioned HR Wallingford to carry out a study to develop guidelines presenting appropriate methods for predicting, and where possible reducing, siltation rates in small communal dams in semi-arid zones in Eastern and Southern Africa. Small dam designers must be able to use these methods; they need simple procedures to carry out assessments rapidly, may not have software skills or computers, and may only have access to very limited local data. A capability to estimate the impact of measures to reduce small dam sedimentation rates is needed to enable the sedimentation lifetime of dams to be estimated at the planning and design stage of small dam projects. This report describes approximate methods for carrying out these calculations. The measures considered are check dams, soil and water conservation measures and sediment bypassing.

Sediment transportation under wind, wave and tidal current

Abstract: According to the theories of the energy dissipation of wave-water and sediment movement and based on the bottom sediment load formula developed by Dou Guoren, a formula to calculate the transport of the bottom sediment, which includes the bed load and part of suspended load, under the joint action of waves, tidal currents and wind-currents is derived. The formula is used to calculate the sudden siltation amount in the access channel of Huanghua Port in the gale period, and the calculation results are close to the measured values.