River floodplain study will generate map for landowners

A study will be done this summer on the river floodplain south of Saskatoon

A comprehensive hydraulic modelling and mapping study of the South Saskatchewan River floodplain south of Saskatoon will provide planners, landowners and developers with solid data on mitigating possible flood damage in the area.
The river floodplain, home to a variety of residences and businesses along Valley Road and the site of several informal recreational spots along the river’s edge, has been a controversial area for development within Corman Park for many years.
Corman Park Council voted at its regular meeting on Monday, April 16 to approve a $131,383 contract with Barr Engineering to conduct a three-phase study, which will be completed by March, 2019.
Half the cost of the study will be covered by the federal government through the National Disaster Mitigation Program – Stream 2: Flood Mapping, administered by Public Safety Canada.
The federal funds will flow to the RM through the provincial Ministry of Government Relations. The RM will pay the full cost of the study up-front, with half the cost being reimbursed by the federal government.
Corman Park council originally recommended such a study in May, 2016, and a formal motion by council to apply for federal funding for the project was adopted in August, 2017. A request for proposals for the preparation of the study was posted online in January, 2018, and a total of 13 submissions by consulting engineering firms were received by the deadline of February 12, 2018.
Corman Park Division 4 Councillor Randy Rooke said the study will provide much-needed data based on factual information.
“I’m delighted to see this finally get underway,” said Rooke. “It’s great to have this being done because it will look not just at elevations, but also take into account things like the flow of water that we can expect to see in different situations. It’s not just the amount of water in a flood incident, the big concerns are the safety hazard and the potential for damage.”
Rooke said there is growing recognition that much of the area is actually in the “flood fringe” because of low water velocity in a flood incident.
The engineering firm will conduct field surveys this summer to supplement existing data and evaluate a one-in-500-year flood event to estimate projected levels and velocity profiles of the flood waters in the river’s main channel and adjacent floodplain.
The model will also calculate the impact of a one-in-50-year, one-in-100-year, and one-in-200-year flood events.
The study will develop Geographic Information Systems (GIS) based flood maps, showing areas where flood depths do not exceed one meter, and where velocities do not exceed one meter per second, at the 1:500 year flow.
The study will also determine the effect of full residential development on the area’s flood storage capacity upstream as well as its backwater effects.
Another goal of the study is to create a “flood hazard map” showing cross-sections, delineated floodway ad flood fringe boundary areas so that Corman Park officials, the public and other interested parties can readily print and read the maps.
The first phase of the study runs from April to June of this year and includes a review of available background information and data, as well as hydrographic survey of the river and ground survey of culverts and other infrastructure.
Phase 2 will run from May to September and involves hydraulic modelling and assessments. The third and final phase is slated from July to December and involves the actual GIS mapping of the flood plain, floodway and flood fringe, as well as a final written report.