Rivers are generally steep and swift, and few are suitable for navigation except in their lower reaches. Although most rivers are less than in length, their rapid flow from the mountains is what provides hydroelectric power. Seasonal variations in flow have led to the extensive development of flood control measures. The longest, the Shinano River, which winds through Nagano Prefecture to Niigata Prefecture and flows into the Sea of Japan, is long.
rivers are generally steep and swift and few are suitable for navigation except in their lower reaches although most rivers are less than in length their rapid flow from the mountains is what provides hydroelectric power seasonal variations in flow have led to the extensive development of flood control measures the longest the shinano river which winds through nagano prefecture to niigata prefecture and flows into the sea of japan is long