Coastal waters

Abstract

The Indian Ocean waters off the Kenyan coast is stratified due to temperature, salinity and pressure differences between the warm less saline less dense surface waters and the deep saline cooler waters. This stratification displays local variations influenced by rainfall or heavy water discharges of the deltas of Tana and Sabaki as well as the monsoon with maximum temperatures during the transition periods of the monsoons when the winds are light and the solar insolation is high. Turbidity increases due to sediment discharges at the mouths of the Tana and Sabaki deltas has been noted with high turbidity during the long rains in April–May and short rains in October–November, the East African Coastal Current transports the sediment northwards to the northern banks with a minimum influence on the water quality south of the coast. Sedimentation rates of 3–4 mg/cm2/day have been recorded from the Galana and Tana deltas where increased concentrations of elements such as Co, Cr, Cu, Ni, Pb, V and Zn have been reported. The semidiurnal tidal regime is influenced by the monsoon winds with the larger waves (>1.5 m) during the southeast monsoons and the lower waves (<1.5 m) during the northeast monsoons. The coastal zone has witnessed an increase pressure from human occupation, mining, agriculture, fisheries and transport and port activities. The coastal ecosystems have experienced shocks linked oil spills in 1988 and 2005 of which evaluations have displayed slow recovery. The export-processing zone is a potential pollutant alongside the industries and mining activities that discharge untreated solid and liquid effluents into the sea. Population pressure has led to urban and informal human settlements that coupled by the lack of knowledge and awareness of the waste management system alongside the impacts of these waste discharges on the environment in the open seas or the mangroves can be postulated to have influenced the water quality although these pollutants have not been recorded to lack of long-term monitoring of the water quality. The establishment of the Coastal Development Authority to coordinate development projects along the coast and the Environmental Management Coordination Act provides an appropriate legal and institutional framework for controlled activities along the coastal region.