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Diffusie van materiaal in stromend water vindt plaats als gevolg van de turbulente beweging van het waxer. dit manifesteert zich in een streven naar het afvlakken van concentratieverschillen met als gevolg uitwisseling van vaste stof en een veranderend lokaal sedimenttransport door veranderende lokale concentraties. In het algemeen zal transport van sediment plaatsvinden op de volgende mogelijke manieren: bodemtransport zwevend transport en spoeltransport. De laatstgenoemde vorm betreft materiaal dat uit de bovenloop van rivieren, de zogenaamde brongebiedenafkomstig is en zonder interactie met het bed wordt vervoerd, dit spoeltransport is daarom niet gebonden aan de hydraulische omstandigheden en is normaliter niet van belang, i.v.m. aanzandingen in de waterloop zelf. Er zou nl. zeer grote vertraging nodig zijn om het materiaal te doen neerslaan; in de hiernavolgende beschouwingen wordt er met deze vorm van transport daarom geen rekening meer gehouden.

The present report deals with the data collected during the survey period form March 11th until March 21th 1986. Elaboration of the survey (analysis, interpretations, conclusions and recommendations of the results) will be elucidated in a separate paper. Chapter 2 deals with the set-up of the survey. Chapter 3 gives a description of the actual situation in Barambai and the results of the water quality measurements. Locations of and periods during which water-levels and velocities were measured are described in chapter 4 and 5. The results of the simultaneous acidity measurements are presented in chapter 6. Chapter 7 contains the results of the electric conductivity measurements and last but not least a description of the levelling and benchmarks is given.

The Huangpu River meanders through downtown Shanghai City and links China's third largest Lake with the Yangtze River estuary. Typhoons passing Shanghai from June to October annually are the main trigger for flooding of the Huangpu River. When storm surges due to a tropical cyclone meet the local astronomical tide, the water levels in the river can easily exceed the warning water levels and cause flooding of the downtown area of Shanghai City. Moreover, during the typhoon season the water levels in the region are sustained higher because of the rain season earlier. As a result flooding of the urban area occurs frequently during the typhoon season. A storm surge barrier in the mouth of the river will effectively keep out high water levels caused by passing tropical cyclones. However, typhoons also bring heavy downpour to the area, which is able to temporarily increase the upstream discharge into the river substantially. The increased upstream discharge because of torrential rainfall triggered by passing tropical cyclones can be a cause for flooding of the river even though the barrier is closed. This study is aimed to determine the flood probability of the Huangpu River during closure of the storm surge barrier as a result of the upstream discharge for the three proposed barrier locations in the mouth of the river. This upstream discharge includes the base discharge of the Huangpu River and the torrential rainfall runoff triggered by the passage of a tropical cyclone. These discharges are investigated as well as their probabilities of exceedance. The situation in which the river is on the verge of flooding is termed the limit state condition. Hence, the flood probability of the river can be expressed as the probability that the upstream discharged water volume during barrier closure exceeds the storage capacity of the river. The storage capacity of the Huangpu River is considered to be deterministic, in contrast with the upstream discharge. The storage capacity is investigated with one-dimensional flow simulations of an enhanced model of the Huangpu River in SOBEK RIVER. The allowed upstream discharges per closure duration, i.e. critical discharge, per barrier location are computed to represent the storage capacity. Subsequently, the probabilities of occurrence of the critical discharges are studied with analyses of the probabilities of the components that build up the upstream discharge. Because of the limited availability of appropriate discharge records, the torrential rainfall runoff distribution is derived from the joint distribution of storm surge and torrential rainfall in the Shanghai area given storm tide levels in the mouth of the river equal to the barrier closure water level. The torrential rainfall probability is related to the storm surge level probability in the mouth of the river; since both are caused by passing typhoons. Therefore, the joint distribution of storm surge and torrential rainfall in the area is investigated with the known distribution of storm surge and torrential rainfall. These individual distribution functions are linked into their joint distribution with a copula. Copulas separate the dependence structure of multivariate distributions with the individual marginal distribution functions. The study of copulas and its applications is rather new but a rapid growing field in the literature of statistics. Eventually the runoff distribution is derived from the torrential rainfall probabilities with empirical runoff relations found from analysis of historical major rainfall events in the area. Prior to the analysis of the torrential rainfall probabilities, the required surge levels for barrier closure are computed by random combination of the tide and storm surge distribution in the mouth of the river. The present warning water level in the mouth of the river is regarded as the future barrier closure level. Subsequently, the required surge level for barrier closure is found by the conditional probability of the surge levels given the barrier closure water level.

Student project report, in cooperation with Smith-Warner International Ltd. (SWIL), Kingston, Jamaica. At this moment the shipping channels in Kingston Harbour, Jamaica, slowly accrete. When the harbour is expanded, the local and global sediment transport is likely to change. During this project it is investigated whether these changes are significant and if they will have a negative influence on the Kingston Harbour area. Also the increase of flood risk for the area surrounding Hunts Bay is investigated. This investigation is done by modeling the hydrodynamics of the Kingston Harbour area with MIKE21 and Delft3D, where after both modeling programs are compared to each other. For the input data for the models, research has been done concerning the boundary conditions. This data is gathered from several projects done in the past about other areas in the harbour and fieldwork in Hunts Bay. During the year, most of the wind comes from the east and south-east direction. There are also two mayor streams which debouch into Hunts Bay, namely the Sandy Gully and the Rio Cobre. Since there is only discharge known about the Rio Cobre (daily values from 1985 to 2010), only the Rio Cobre is taken into account. The maximum measured value was 563 m3/s (during hurricane IVAN) and the average value is about 12 m3/s. For the sediment input data some fieldwork is done in Hunts Bay to gather information about the type of soil. From this it is concluded that it is silt, which is confirmed after a lab research of the sediment. However these accurate soil properties couldn’t be implemented into the models due to the lack of time. During the fieldwork also a bathymetric survey was done, which showed that Hunts Bay is sedimented compared to the previously used bathymetric data, gathered from admiralty charts in 2000. Calibration of both models is done by comparing it with the measured water level and flow velocities underneath the Causeway Bridge. Since this is the only point where data was available for, the calibration kept global, and should be improved in the future. The modeling showed that most of the sediment transport into the shipping channel is caused by the high discharge of the Rio Cobre. Ivan showed the most extreme sedimentation and the biggest change due to the expansion. In the present situation the shipping channel is gradually silting, with two areas where the siltation is concentrated. With the first phase expansion these ‘mountainous’ areas will be much more concentrated. However it can be concluded that the changes in the sediment transport due to the first phase expansion are not significant and will not lead to more problems than there are without this expansion. For this problem a sediment trap is proposed. At first it was placed just eastward of the Causeway Bridge, but this didn’t solve the problem and it would be in the way for the phase two expansion. Therefore a sand trap is designed in Hunts Bay, just westward of the Causeway Bridge. This location is really effective, since it stores the sediment from the rivers. This solution prevents the shipping channel to silt. Again, since the lack of reference data, on the size of the pit nothing can be said.