Reclamation shifts the evolutionary paradigms of tidal channel networks in the Yellow River Delta, China

摘要

Tidal channel networks are ubiquitous features of coastal landforms that control the input and output of intertidal water, sediment and nutrients. Nevertheless, those intertidal platforms have undergone extensive losses due to human activities such as land reclamation. Identifying how tidal channel networks respond to land reclamation is critical to our prediction of the fate of residual tidal landforms. However, the morphological changes in the channel networks in the Yellow River Delta (YRD) impacted by severe reclamation remain unclear. Here, we analyzed the spatiotemporal dynamics of channel networks on two scales (the delta scale and the zone scale) under the double stress of land reclamation and natural pressure by comparing a comprehensive suite of morphological channel characteristics, including channel segment count, channel order, length, fractal dimension, drainage density and drainage efficiency. The results show that the interannual dynamics of tidal channel networks in the delta over the last three decades have experienced two periods: a favorable period during 1984-2000 and an adverse period during 2001-2018. The spatiotemporal patterns of channel networks varied with zones. Land reclamation exerted a dominant influence on shifting the evolutionary trend of channel networks on both the delta scale and the zone scale when reclamation proportion exceeded a certain threshold. Sediment siltation could to a certain degree mitigate the impact of reclamation on tidal channel networks development. Our study highlighted the effect of reclamation on the geomorphological evolution of tidal channel networks and identified its impact threshold which could further be used to guide coastal zone restoration and management.