Although the scenery of Amanohashidate is entrancingly beautiful, the quality of water in the Aso-kai and Miyazu Bay across the Amanohashidate has been increasingly polluted due to the delay of sewage work in Noda-gawa River system, which flows into Aso-kai.
天橋立の風光明媚さとは裏腹に、野田川水系の下水道整備が遅れたため、阿蘇海に流入する川の水質悪化にともない、阿蘇海や天橋立をはさむ宮津湾でも水質汚濁が進んでいる。