Analysis of Hydraulic Characteristics in the River Mouth with Large Tidal Difference – ADCP Application

摘要

Hydraulics of the river mouth with a tidal effect and saltwater intrusion is sometimesrnquite different from that of the river without them. The Han River, the largest one inrnKorea, has a very wide river mouth connected directly to the sea with a largest tidalrndifference, nearly a 10m at its maximum. This induces some interesting hydraulicrnphenomena such as the tidal bores of 1-2m high, large diurnal changes of water stagernand velocity, uneven distribution of the flow velocity in the river cross section, andrnchanges in the local flow velocity due to the mixing of freshwater with saltwater.rnBecause of these, it is usually difficult to measure the flow field in the river mouth byrnusing the ordinary methods. In this study, ADCP(Acoustic Doppler Current Profiler) hasrnbeen used to measure the three-dimensional characteristics of the flow field in thernmouth of the Han River. The ADCP used for this study is the one developed by RDrnInstrument Company.rnIt has been revealed by the measurement that the water stage, velocity, and discharge inrnthe river mouth vary greatly without a change in the upstream flow. At a tidal differencernof 9.79m, the reverse flow from the downstream to the upstream produced thernmaximum local flow velocity of –1.0m/s and the maximum water discharge of –rn1,620m3/s. At the same day, the ordinary flow from the upstream to the downstreamrnproduced the local flow velocity of 1.0m/s and the water discharge of 1,490m3/s. Thernfreshwater discharge from the upstream during the measurement was only aboutrn300m3/s with the average velocity being less than 0.3m/s. Another interesting fact foundrnby the measurement was that the reverse flow occurs in the vertical direction, with a