For loading and unloading of boats or ships round the clock, the access channel and its expanded part-a port are excavated on the lagoon and ocean reef flats in the tropic Pacific oceanic islands. Without moles, the a...For loading and unloading of boats or ships round the clock, the access channel and its expanded part-a port are excavated on the lagoon and ocean reef flats in the tropic Pacific oceanic islands. Without moles, the access channel port traps sediment and further transports it to the ocean or lagoon, resulting in coastal erosion. The wide uneven reef flat with a large catchment area tends to cause the formation of tide currents in the channel port, while strong waves on the narrow even reef flat can give rise to rip currents. An access channel port with a mole on one side or two moles on both sides results in less erosion. A model is recommended as an artificial harbor on the ocean coast, which is an excavated port surrounded by a mole, connected with the ocean by an access channel and with the shore by a bridge shaped pier.展开更多
Wind data spanning 28 years （1977-2004） from four meteorological stations （Tanga, Zanzibar, Dar es Salaam and Mtwara） were analyzed to elucidate the effect of winds on coastal erosion along the coast of Tanzania. ...Wind data spanning 28 years （1977-2004） from four meteorological stations （Tanga, Zanzibar, Dar es Salaam and Mtwara） were analyzed to elucidate the effect of winds on coastal erosion along the coast of Tanzania. The investigation entailed wavelet analysis of the time series of winds which were related with past erosion events at each site. The study also analyzed qualitatively the incidences of tropical storms in relation to coastal erosion events along the coast. The results revealed that most of the critical erosion incidents in the past few decades were associated with periods of occurrence of extreme wind speeds and tropical storms. Furthermore, the results indicated that the wind speeds and the frequency and intensity of tropical storms had generally been increasing during the past three decades. The findings were consistent to those recently reported for the coast of Dar es Salaam. The increasing trends of winds and storms are considered to have direct impact on the wave climate with increased risk of shoreline wave-induced erosion that is already affecting relatively many parts of Tanzania.展开更多
基金funded by the Ministry of Foreign Economic Co-operation and Trade,China.
文摘For loading and unloading of boats or ships round the clock, the access channel and its expanded part-a port are excavated on the lagoon and ocean reef flats in the tropic Pacific oceanic islands. Without moles, the access channel port traps sediment and further transports it to the ocean or lagoon, resulting in coastal erosion. The wide uneven reef flat with a large catchment area tends to cause the formation of tide currents in the channel port, while strong waves on the narrow even reef flat can give rise to rip currents. An access channel port with a mole on one side or two moles on both sides results in less erosion. A model is recommended as an artificial harbor on the ocean coast, which is an excavated port surrounded by a mole, connected with the ocean by an access channel and with the shore by a bridge shaped pier.
文摘Wind data spanning 28 years （1977-2004） from four meteorological stations （Tanga, Zanzibar, Dar es Salaam and Mtwara） were analyzed to elucidate the effect of winds on coastal erosion along the coast of Tanzania. The investigation entailed wavelet analysis of the time series of winds which were related with past erosion events at each site. The study also analyzed qualitatively the incidences of tropical storms in relation to coastal erosion events along the coast. The results revealed that most of the critical erosion incidents in the past few decades were associated with periods of occurrence of extreme wind speeds and tropical storms. Furthermore, the results indicated that the wind speeds and the frequency and intensity of tropical storms had generally been increasing during the past three decades. The findings were consistent to those recently reported for the coast of Dar es Salaam. The increasing trends of winds and storms are considered to have direct impact on the wave climate with increased risk of shoreline wave-induced erosion that is already affecting relatively many parts of Tanzania.
