This study aims to examine the regional impacts of the construction of a long submerged floating tunnel across the bay. This study has been motivated by the apparent scant data and research works on the likely regional consequences of such a large-scale project (Alex 1989; Thirumurthy 1987). The main concern is with the department of techniques to predict likely regional impacts. The main premise is that the construction of submerged floating tunnel across the bay will result in changes may initially affect the immediate surroundings of the project site but eventually they are likely to have widespread effect. Ideally, these changes may be advantageous to some organism but disadvantages to others. From this view-point, we purpose an System Dynamic Model for the regional impacts. The actual simulation is examined using the example of the Volcanic Bay of Hokkaido in northern Japan.