The role of tides, river discharge and wind on the residual circulation of Maputo Bay

Abstract

Lateral variability of residual flow was investigated in Maputo Bay in Mozambique, Africa. The bay is nearly rectangular with 30×30 km, mean depth of 5 m. The bay mouth is ∼18 km wide with mean and maximum depth ∼10 m and 30 m, respectively. Tides ranges between 1 and 3 m at neap and spring tides, respectively. The mean annual river flow is ∼225 m3/s, ranging from ∼150 to ∼400 m3/s during winter and summer, respectively. Southeasterly (SE) wind are the most frequent wind during the year followed by northeasterly (NE) winds. In order to scale the relative importance of tides, wind and buoyancy effects on the residual exchange flows, we designed three-dimensional numerical experiments (Delft3D). Results show strong changes among the scenarios and between neap and spring tide conditions. During spring tide, flows becomes more vertically homogeneous and laterally sheared, modulated by the cross-section shape. Most important exchange flows were during neap tides mainly with scenarios forced by tides. There are some locations prone to entrap sediments, such as the inlet of the Incomati river and to the north of Inhaca Isle.