Complex sentence: Much mud was laid down by river and tide during the disused period from 1986 to 2015 and some mudbanks need minimal adjustment to accommodate the movement and docking of boats with no impact on the nature of the river.
Split into simpler sentences: Much mud was laid down by river and tide during the disused period from 1986 to 2015. Some mudbanks need minimal adjustment to accommodate the movement and docking of boats with no impact on the nature of the river.