The effect of the construction of a large-scale marine structure in Osaka bay is evaluated using Landsat TM data. Sea surface temperature and chlorophyll before and after building the Kansai international airport are made from the satellite image. Since the conventional formula underestimates the concentration of chlorophyll in this area, we derive a new formula. The flow stagnation around the airport, clockwise stream in the bay, a large plume in the western area is observed.