Shore Morphology and Sediment Characteristics South of Pangani River, Coastal Tanzania

Abstract

Shore morphology and nearshore sediments between the Pangani and Kipumbwi
rivers in coastal Tanzania were investigated. The information was gathered using field
observations, sediment sampling of the area, and interviews with Pangani residents. The
distribution of sediments on the sea bottom is mainly controlled by bathymetry, with sand
(medium- to coarse-grained) dominating water depths less than 10 m, and silt dominating depths
greater than 15 m. Sediments in water between 10- and 15-m depth consist of a mixture of fine
sand and silt. The carbonate production in the study area is limited by the high influx of
siliciclastic sediments from the Pangani, Kipumbwi and Ushongo Mabaoni depo-centres.
While previous studies attribute the disappearance in the 1970s of Maziwi Island off the
Pangani River mouth to sea level rise, the present study argues that anthropogenic influences
may have been the major cause; if indeed the vegetation on the island was cleared as is reported,
this could have hastened its disappearance. Sea level rise is also considered to be one of the
potential threats to the survival of small islands like Maziwi.

Keywords: shore morphology, sediment, Pangani River, Tanzania

West Indian Ocean Journal of Marine Science Vol. 3 (2) 2004: pp. 93-104