The city of Edmonton gets approximately 14 inches of rain each year, mostly from thundershowers, which can drop a large amount of water in a condensed area, in a short period of time. When a major rainstorm hits, the sizable volume of water that occurs can overwhelm drainage systems and cause flooding. Rapid snowmelt in the spring can also pose a similar risk. During rainy weather, the pressure on your home drainage and the municipal drainage systems increases dramatically. The condition and capacity of these systems are equally important in managing the wet weather. Blocked or broken pipes, poor lot grading, excess hail and other factors can restrict the flow of water, substantially increasing the risk of flooding.
For nearly 30 years, the City of Edmonton and the National Plumbing Code of Canada have required that each new home has a backwater valve to protect against sewer backup. Downspout extensions or splash pads are also recommended. Downspouts are hollow pipes that take water from the gutter and channel it to the ground. In Edmonton, it must end at least six inches inside your property line. Often, homes that flood are missing one or more of these components, or the components are found to be in poor working order. The location of a home can also make a difference. For example, homes built in low-lying areas or next to lakes have a greater flood risk, as surface and groundwater will naturally drain to these areas. Keep in mind, a long downspout extension is of no value when it’s propped up against the side of the house. In Edmonton, the municipal stormwater drainage system design standard is one in five years and is based on historical weather patterns. This means the system can handle any typical rainstorm but could have its capacity exceeded, on average, once every five years.