P4G green network study area: Drainage Pilot Project

At its November 16, 2017 meeting, the P4G Regional Oversight Committee (ROC) discussed the potential to align a number of drainage studies that are needed in portions of the P4G Regional Plan area with refinement of the Green Network Study Area (GNSA).  At the April 20, 2018 meeting the ROC endorsed a pilot project subject to municipal budget support.

An area in the northern part of the R.M. inside and outside the P4G study area was selected for the pilot project; a map of the study area can be found HERE. Engineers from Saskatoon Water were the lead on the analysis, modelling and mapping on behalf of P4G.

Existing LIDAR data was cross referenced with a survey of culverts and other data to create catchment areas. The model was calibrated to historical studies of the watershed areas, before it was ran to map drainage paths and evaluate the extents of the flooded areas within the GNSA. The final report describes the general hydraulic conditions of the system during a 1:100 year storm event, including flood depths, hazard classification and flow rates.

The study conclusions were:

•    Areas within the GNSA should not be developed without improvements to the drainage and consideration for existing flood depths, flow rates and existing flow paths;
•    Outside of the GNSA bounds, flow areas and flow pathing between them should not be obstructed by development;
•    Low lying areas and connecting flow paths should be considered for storm water retention and conveyance;
•    Development should not increase the flow into the GNSA in order to maintain the predicted flood boundaries and levels; and
•    The GNSA system should be considered when upgrading infrastructure as culvert capacity and location may affect the upstream and downstream flood bounds.

This pilot project provided an opportunity to produce the first layer of much needed drainage analysis that could be used as a template for further GNSA analysis and guide development decisions in the P4G Region going forward. Refinement of the remainder of the GNSA within P4G, including ecologically sensitive areas and the viewshed of the Wanuskewin Heritage Park, is being completed under the Natural Areas screening project. The results of the GNSA Pilot Project will be combined with that work to recommend areas of potential refinement to the GNSA.  This may confirm or recommend modifications to the boundary.  The results of that are expected in 2020.

Please contact the R.M. Planning Department with any questions or for more information on the pilot project. The information contained in this study is recommended for consideration for any development applications within and adjacent to the study area.