Here a couple of suggestions: First, decide which civil engineering project you are going to write about. Do some research on when and how the project was accomplished. Research why the project needed to be done in the first place. Your question has the word canal in it. Which canal? Why was it needed? Who was going to benefit from its completion? What where the challenges to building it? Who paid for it? Does it still exist today? Has it been changed or modified since its initial construction?
Once do you some research on the project then you can organize the information into an essay. It would make logical sense to write about the project chronologically: the need, the plans, the actual construction, the final results and the current status.