Reaching the sewer entrance | Mission 7 - The Flooded District Dishonored Guide
Last update: 11 May 2016
New Main Quest: Find a way through the sewer to the pub
Go ahead and turn left.. DO NOT SMASH the wooden boards because this will draw unnecessary attention from weepers to you. Apart from that, even if you eliminated them, apart from small quantities of gold and food, you wouldn't gain anything interesting.
It is a way better idea to take the entrance to the building on the left, shown in the above screenshot. Explore the building to find a bone charm. You are up for some climbing here but, eventually, you will end up in the same area that you would be in if you destroyed the boards.
Follow the quite linear path. After you reach a bit larger area, go down and explore the location for ammo, Sokolov's health elixir and Piero's spiritual remedy. Finally, interact with the handle shown in the above screenshot. Quickly jump into the hole to reach the [Old Dunwall Sewer].