Between 1979 and 1995, the delta grew into a southeast-bending arc, about 15 km (10 mi) wide. By 2000, the tip of the delta had eroded away, as a newly-cut channel diverted the river’s flow to the northeast. The 2015 image shows that the river continues to deposit massive amounts of sediment into the Bohai Sea while it builds the new delta.
The Yellow River is the most sediment-rich river in the world, carrying 1.6 billion tons of silt annually. It is the second longest river in China, stretching 5,500 km (3,400 mi) over 9 provinces before emptying into the Bohai Sea, near the city of Dongying in Shandong province. The river picks up silty sediment, called loess, as its middle section flows through the Loess Plateau. Loess is pale, dusty when dry, and potentially fertile – but highly erosion-prone. One billion tons of this yellow sediment deposits along the river’s lower reaches and at its mouth every year, expanding the Yellow River Delta and reshaping the coast. Besides natural causes, flood management strategies that include the construction of dams, seawalls, and jetties have had a direct impact on the river’s water discharge and sediment load flow into the ocean. Other human-induced changes such as agricultural development and population growth also play a key role in contributing to the coastal delta’s transformation. Research shows that the area of the Yellow River delta grew by 330 km2 from 1976 to 2009. Researchers have relied on Landsat imagery to locate and quantify these landscape changes.
Since 1972, the Earth-observing satellites of NASA and USGS’s Landsat program have imaged the planet’s land surface. The successive satellites have collected the longest continuous dataset of its kind. The above demo is just one of many uses of Landsat imagery to track regional landscape changes, both natural and artificial. Find me on Twitter @bluebweee or hit us up if you have any questions.
Images were taken by Landsat 3 on May 27, 1979; Landsat 5 on August 24, 1992 and May 29, 1995; Landsat 7 on May 2, 2000; and Landsat 8 on May 4, 2015. Via https://www.mapbox.com/blog/tracking-changes-with-landsat/