<p>Environmental issues related to reservoir impoundment of hydropower stations are long-standing causes for concern, including the development time effect, spatiotemporal evolutionary principles, and assessment of susceptibility to geological disasters. Accordingly, we investigated the Miaowei Hydropower Station on the Lancang River, China, as a representative example. A dynamic susceptibility assessment model for geological disasters was constructed by combining the information quantity model and grey correlation method. The model was based on the spatiotemporal evolutionary principles of induced disasters, with the dynamic change of the water storage level per unit year as key indicator factor. The development time effect rule of disasters was clarified, with our results indicating that 36 events were induced by reservoir impoundment. Analyses indicated the first impoundment period, first year of water storage, second and third years of water storage, and reservoir operating stage as the initial, peak, frequent-occurrence, and low-incidence periods of induced events, respectively. The spatial development characteristics of the observed disasters were successively classified as sporadic distribution at the reservoir head, uniform distribution across the reservoir, intermittent distribution across the reservoir, and irregular sporadic distribution. Our dynamic susceptibility assessment model exhibited relatively high accuracy. The development time effect of induced geological disasters was 3–4&#xa0;years during the initial stage of reservoir impoundment. As normal operations continue, the incidence of geological disasters will decline and the development of existing geological disasters will stabilize. Our results have significance for predicting, investigating, and preventing induced geological disasters in the Lancang River high mountainous and canyon regions.</p>