Earth observation-based coastal zone monitoring of the Yellow River Delta: Dynamics in China's second largest oil producing region over four decades

The largest challenge for the Yellow River Delta region is finding an equilibrium between its two largest assets: large, valuable wetland reserves rich in biodiversity, declared as Ramsar sites in 2013 and breeding and resting grounds for numerous migratory bird species on the one hand, and extensive industrial and urban development based on the wealth of large underground oil and gas reserves, on the other. Based on high and highest spatial resolution satellite imagery covering nearly four decades, we employed manual feature digitization as well as rate-of-change statistics automatically derived with the Digital Shoreline Analyses System (DSAS) and present oil-industry-induced river bed changes and related coastal dynamics manifested via land erosion or accretion, and thus overall changes in the appearance of the Yellow River Delta. Over the past 37 years large re-diversions led to net erosion areas with over 13 km of shoreline retreat, and net accretion areas with over 21 km of shoreline advance. The satellite data furthermore enabled an assessment of oil pump development in the delta for the past two decades, indicating a strong expansion of oil extraction activities even in two of the delta's protected nature reserves, taking place at times and locations that indicate noncompliance with national regulations. Overall, the study proves the power of satellite imagery to quantify changes in the coastal zone, and to detect industry related activities; including the monitoring of compliance to restricting regulations. It is especially the freely accessible Landsat archives, granting four decades of monitoring, which are of immeasurable value to depict the regions dynamics. With Landsat 8 already in orbit and with the upcoming launch of the Sentinel-2 satellite, the monitoring concept presented here can be continued into the future.