Why Homes Flood

On average, the Town of Slave Lake gets 362 mm (14 inches) of rain every year. Most of this comes in the form of thundershowers or summer storms, any one of which can drop a large amount of water in a concentrated area in a short period of time. When a major rainstorm hits, the huge volume of water that occurs can overwhelm drainage systems and cause flooding. Snow poses a similar threat in the spring if there is a rapid snowmelt. 

During a rainstorm, the pressure on your home drainage and the municipal drainage systems can increase dramatically. The condition and capacity of these systems are equally important in managing 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. 

When the volume of stormwater exceeds the municipal system’s capacity, surface pooling occurs. Some of this excess water also finds its way into the sanitary sewer system. This creates added pressure on sanitary pipes, including those exiting from homes. Since 1988, The Town of Slave Lake has required that each new home have a backwater valve to protect against sewer backup. 

Lot grading must have a positive slope of 5% for at least 3.0 m (10 ft.) away from the building’s foundation or to property line, whichever is less. Also note that grading near a common property line must not impact adjacent lots. Also, downspout extensions or splash pads, window wells (where required) and weeping tile connected to a sump pit (in some cases) are recommended. 

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. 

Other flood risk factors include lot elevation, water near a foundation style of home, servicing elevation, surface conditions and water drainage from neighbouring properties. 

Property owner’s behaviour during a storm can also increase the risk of flooding. For example, washing clothes, taking a shower, running the dishwasher and flushing your toilets adds water to a system that may already be overloaded. 

The water may have nowhere to go but up your floor drain and into your basement. This is particularly true if you do not have a backwater valve. The valve is designed to close during extreme conditions and keep outside water from getting in. When this happens, water from the inside also can’t get out. 

Many people forget to put their downspout extensions down before it rains. A long downspout extension is of no value when it’s propped up against the side of the house. If you have a sump pump, double check to see that it is plugged in and the breaker is on during a storm. More than one homeowner has searched for the cause of a flooded basement only to discover the sump pump lacked the power to perform.