Intergovernmental oceanographic commission (of unesco) information on eastern african sea level



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The morphology of the coastal zone in Sofala Bank is characterised by flat land with an almost continuos fringe of mangrove swamps. These swamps are associated with main rivers and with tidal creeks. These only carry freshwater during the rainy season. Bare soil flat of varying width separates the mangrove forest from the terrestrial forest.



The bottom in the central and northern Sofala Bank is flat and mostly muddy. It is where most of the industrial fleet operates. The southern Sofala Bank is characterised by sandwaves thought to be due to strong tidal currents mentioned above (Stre and Paula e Silva, 1979 and Brinca et al., 1982). The wavelength of those sandwaves ranges between 200 and 400 m and the height varies from 10 to 15 m, and in some cases exceeds over 20 m. The bottom is thus inappropriate for bottom trawl, save near the shore where semi-industrial fleet and artisanal fisherman operate mainly bottom trawls and beach seines, respectively, and fishing mostly shrimp.
Sofala Bank is mostly dominated by the Southeast Trade Winds (Stre and Jorge da Silva, 1982). Winds are mostly from NE - E - S. SE trade winds winds, with frequencies above 20%, occasionally exceeding 30%, and with the mean monthly force above 3 m s-1, are the most predominant. The southerly winds are the strongest, with the mean monthly force exceeding 5 m s-1 during September and January.
The rainy season last from November to May. The annual rainfall is about 1140 mm. In the southern Sofala Bank the evaporation is about 1650 mm per year, thus the evaporation prevails over the precipitation by about 500 mm per year, on average.
Most of the rivers of Mozambique enter the sea through Sofala Bank. The annual runoff of the all-Mozambican rivers is estimated to be 141 km3, and the rivers within Sofala bank contribute with about 85%. Zambezi River, the most important river in Mozambique, contributes with 67% for the total of all rivers. The Púngoe, which passes through Beira is shared with Zimbabwe and contributes with about 3.3 km3. Other important river in the vicinity of Beira is the Búzi river, which contribute with about 6.7 km3 of water per year.



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