Ottawa's road suffer from harsh winters. Potholes are common, especially in the second half of winter and in early spring.
Besides potholes, you can get stuck in cracks that can grab bicycle wheels or grates or other ironworks that are missing, or broken, or surrounded by missing asphalt. Rain and melting snow can hide potholes and clogged drains. Don't ride through puddles.
Your best defense is to look ahead, ride at least 1 metre away from the curb (avoiding many of the problems), and ride around, not over, potholes, cracks or ironworks. A cycling traffic skills course (offered by the City of Ottawa) will also teach you how to dodge potholes.
And any time you see one of these, please report it so it gets fixed at the City of Ottawa's pothole report page (The webpage contains an option to upload a photo and to pinpoint the exact location on a map).