The tallest waves and most devastating flooding from the 2011 Tohoku-oki tsunami occurred along the jagged coast of northern Honshu, a landscape dimpled with bays and coves known as ria coast. The steep, narrow bays of ria coasts trap and focus incoming tsunami waves, creating destructive swells and currents that can push huge volumes of water far inland, particularly along river channels.
That's exactly what happened in the days before the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), an instrument onboard NASA's Terra satellite, captured this image of flooding along the Kitakami River in Miyagi Prefecture. Taken on March 14, 2011, the false-color image combines infrared, red, and green wavelengths in a way that makes it easy for the human eye to distinguish between water and land. Vegetation appears red and fallow fields appear pale brown. Floating debris from the tsunami, which appears gray, has accumulated in several coves along the coast, particularly in the lower right of the image.
Wide swaths of flooding on the both the north and south banks of the river channel are visible, as well as sediment at the river's mouth. Some of the most dramatic flooding occurred just to the south of the river—where floodwater washed across large tracts of farmland—and in the small village of Nagatsura, situated on the northern edge of an inland cove. Notice how far up the river extensive flooding occurred: Research conducted by scientists at Tōhoku University suggests that waves from the tsunami traveled nearly 50 kilometers (30 miles) upstream from the mouth of the Kitakami River.