Effect of fractional vegetation cover on the evolution of tidal creeks of the Jiuduansha shoal in Yangtze River Estuary (China) during 1996-2020

The Jiuduansha shoal (JDS, in Yangtze River Estuary, China) is a national nature reserve. Understanding the relationship between fractional vegetation coverage and tidal creeks is significant to the JDS protection. In this study, the distribution of tidal creeks and fractional vegetation coverage in JDS were extracted and analyzed based on long-time series Landsat and HJ-1A multispectral images during 1996-2020. The results indicate that the total length of tidal creeks increased by 11.71 km/a during 1996-2020. The vegetation coverage increased by 4.79 km²/a. In 2020, the highest order of tidal creeks was fourth. The distributions of tidal creeks were closely related to high vegetation coverage areas. Among the different orders of tidal creeks, those at the first order significantly affect the overmarsh path length (L_OP). Among the different vegetation coverage parameters, the impact of the vegetation coverage area on the L_OP was most remarkable. The relationship between the L_OP and vegetation coverage area satisfied an exponential function. As the vegetation coverage area increased, the L_OP gradually decreased. The drainage efficiency of the creek network increased.