DEPOSITION RATE OF SEDIMENT IN A RIVERINE-TYPE MANGROVE AREA UNDER ENVIRONMENTAL IMPACT FROM INLAND

Abstract

To clarify the deposition process in a riverine-type mangrove area which is directly influenced by terrestrial water with rich nutrients and high suspended-sediment concentration (SSC), we have conducted field measurements on suspended-sediment transport and deposition process in the Miyara River, Ishigaki Island, Okinawa, which has a typical riverine-type mangrove forest. The observed SSCs in the swamp are relatively lower than those in the creek under hydrologic events. The observed results reveal that the accretion rates of ground level are 3.1 and 1.3 cm/year in the upstream and downstream regions of the swamp, respectively. These facts demonstrate that the deposition rate of sediments are dominant in the upstream regions due to the huge environmental impact from inland and the mangrove swamp may capture a large amount of suspended sediments.