Natural environment and activities in watershed unit have nurtured diverse ecosystem. Social or economic change could declined the diversity of watershed as a green infrastructure for the city. Especially large-scale natural disaster hasten the social change. This study aims to develop planning method of green infrastructure based on the water management in watershed for shrinking cities. To evaluate vulnerability and sustainability of watershed environment, we construct the database of the former agricultural waterway, and analysed the features by division of former city district, as environmental unit of the agricultural society, and sequence of the waterway network and opens paces and public facilities. Furthermore we discussed the stakeholder who can manage the green infrastructure in daily life and tourism or recreation aspects.