A consultant has recommended building dikes on the west side of Maple Creek, Sask., to avoid flood damage similar to what occurred last summer.
Ray Pentland, president of Water Resource Consultants Ltd., said the 2010 flood was a one in 3,700 year event.
“The actual rainstorm that was the immediate cause of the flood was a moderately big rainstorm … a one in 100 year event,” he said.
“It wouldn’t normally have caused that big a flood except the spring runoff last year was moderately heavy so all the reservoirs and sloughs were full of water.”
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He said dikes are not generally the best form of flood protection available but in this case they are the only option.
The town is on a flood plain and a large flood irrigation project lies to the south.
“Really, the practical engineering solution for flooding in Maple Creek is to build some dikes along the west side of town to keep the creek from flooding into town,” he said.
The dikes would be two metres tall at the highest point and about a kilometre long.
Pentland said construction could begin now on temporary dikes in anticipation of potential flooding this year.
He also said it’s unlikely the current snow pack could lead to significant flooding.
“To get that kind of flood you really need a rainstorm event,” he said.
“The one redeeming thing is that April rains can’t be as heavy as June rains. The energy that drives rainstorms just isn’t there.”
The Saskatchewan Watershed Authority and Agriculture Canada commissioned Pentland’s report after excess moisture and a June rainstorm combined to flood the town and nearby rural properties and wash out a section of the Trans-Canada Highway.
Several other urban centres were flooded during the summer, and agricultural land is still saturated.
Premier Brad Wall announced Jan. 31 that a $22 million flood prevention program would be available to help communities and residents prepare for possible spring flooding.
Clinton Molde, watershed authority manager in Weyburn, said individual rural residents may be eligible for funding through this program, as is Maple Creek.
Pentland’s report also examined the role that several small irrigation reservoirs near Maple Creek played in the flood.
The McDougald, Harris and Downie reservoirs are all upstream of Maple Creek, off main channels and supplied by canals running from creeks.
The reservoirs, which are operated by Agriculture Canada’s agrienvironmental services branch, were already full when the rainstorm hit.
Pentland said the reservoirs were never designed for flood control. They did divert as much water as they could through the canals but had little impact on the town.
Another reservoir downstream, Junction Reservoir, helped take away some of the peak flow.
He said that if the town chooses to construct permanent dikes, it must maintain them forever.
Gophers could dig tunnels through them, which would lead to many breaches.
“The dike itself is a perfectly safe structure but they occasionally fail because they aren’t maintained because people forget about them,” Pentland said.
Maple Creek experienced significant flooding in 1998 and 1955.
Pentland couldn’t say why dikes had not been built earlier.
