Flood Scoping Study for Highwood and Little Bow

Update July 18, 2019

Phase 2 of the Scoping Study

With funding provided by Alberta Environment and Parks, Foothills County has been able to complete Phase 2 of the Scoping Study. This work included hydraulic modelling and modelling support on both the Highwood and Little Bow Rivers.

On the Little Bow River: A bathymetric survey and modelling support were undertaken to incorporate design changes to the proposed South West Dike and improve low-flood accuracy of the Little Bow River two-dimensional (2D) hydraulic model. This model was developed to examine flood-related areas of concern on the Little Bow River upstream from the Twin Valley Reservoir subsequent to mitigation works being constructed to protect the Town of High River after the June 2013 flood event. The final report is provided below.

Bathymetry Survey and Modelling Support for the Little Bow River

On the Highwood River: Additional modelling was undertaken to incorporate the design changes to the south west dike and to make refinements to areas of uncertainty in the previous hydraulic model of the Highwood River. The final results of the modelling can be found below:

2019 Modelling Results for Phase 2 of the Scoping Study for the Highwood River

It should be noted that the post mitigation condition for both studies was the 55A flood mitigated scenario. The Town of High River's application to the Province for the South West Dike was based on the 53A scenario. Both scenarios include the updated s-curve configuration for the south west dike. Following is an explanation of the difference between the two scenarios taken from Table 1 in Appendix 1 of the Bathymetry Survey and Modelling Support for the Little Bow River report:

Scenario 55A: Complete mitigation scenario that includes all mitigation measures included within Scenario 53A but with their representation within the model updated to reflect as built survey. This includes at minimum the inclusion of all topographic changes that have occurred on the unprotected side of the Town Levee System. In addition to model changes to better represent dikes further model upgrades were made to incorporate the as-constructed Centre Street upgrades, finished surface elevations associated across Wallaceville, and changes to channel bank elevations associated with completed scour protection measures.