August 5, 2016 Leave a comment
Nobody ever thinks that the ditches that parallel municipal rural roads provide useful environmental services, but they should, because they do. They are mini wetlands.
Here is evidence that wetland plants thrive in an easily observable 450 metre length of roadside stream on the north side of Highway 11A on the west side of the Town of Sylvan Lake:
Municipal ditches can function as mini wetlands
See this photo album for more detail on the types of aquatic plants and grasses that thrive in this section of ditch even in the 2016 season that has received just average precipitation. This ditch discharges into Golf Course Creek immediately upstream of Marina Bay and provides nutrient sink and filtration of surface water flow off agricultural land to the west. The width of the ditch is about 5 metres so this mini wetland area is 2250 square meters, or 0.22 hectares.
A survey of the numbered rural roads in the rest of the Sylvan Lake watershed shows that a grid of 122 kilometres of roadway crisscrosses the watershed and forms part of the surface water drainage system that delivers runoff into Sylvan Lake and affects water quality.
Municipal roadside ditches are part of the watershed drainage system that discharges into Sylvan Lake
Since the adjacent ditches occupy 10 metres of land (5 m on each side) per metre of road, the total municipal wetland area is 1.2 million square metres, or 122 hectares. That area is much greater than that of the minor natural wetlands (see the blue ponds in the graphic), some ephemeral, that are scattered throughout the Sylvan Lake watershed.
Since the land area in the watershed is about 10,800 hectares, the municipal ditches or mini wetlands occupy 1.1% of the land area. That is enough to justify more careful scrutiny of ditches and their environmental services. Segments of the in-watershed municipal road system should probably be managed as the beneficial mini-wetlands that they are, and not damaged by maintenance practices during critical periods of the surface runoff and plant growing seasons.