In 1776 the commissioners raised an additional £2,000, with which they hoped to construct a new lock at Thornham Bottoms, below Snakeholme, and to dredge the river below that. Instead they opted to convert Snakeholme lock into a two-lock staircase, which allowed vessels to use it over a greater range in water levels. Plans to extend their powers below Aike Beck, so that Hull Bridge at Tickton could be made larger were thwarted by Beverley Corporation in 1777, but some dredging of Frodingham Beck took place. The first recorded dredging between Emmotland and Aike Beck took place in 1783, and subsequently dredging was a prominent item in the accounts. The expected dividends of 5 per cent did not materialise, but dividends were paid in most years after 1774, starting at 1.5 per cent and rising to 4 per cent by 1790. By 1784, the navigation was making enough profit for the commissioners to build a warehouse and granary at Driffield.