The levee along Edogawa or Edo river is 10m or 30 ft. above the river course. The land on the other side is near sea level. The population density for this Tokyo ward is 13,900 people/km² or 35,900 people/sq. mi. Millions of people are protected from riverine flooding by these structures. This image is from Earth, Water, Fire, Wind, Emptiness: Tokyo Landscape. Click on the image for a larger view.