The 4th annual Ottawa International Walking Festival is scheduled for the weekend of October 22nd and 23rd. It includes a wide range of walking events with various distances (5, 10, 15, 32 kilometre and a half and full marathon).
It sounds like a great event. Bring your most comfortable and supportive walking shoes. And if you are a Nordic Walker bring your poles.
I am a great fan of walking as a key part of your exercise program. I encourage many of my clients to incorporate walking into their day.
The Festival has a website with all of the information you need including registration.