Fort Macleod is in southeastern Alberta along the banks of the Oldman River and near the confluence of Willow Creek and the Oldman River. The Oldman River has experienced large floods in the recent past, including 1975, 1986, 1991, 1995 and 2013. Through a competitive tender, Alberta Environment and Parks (AEP) retained NHC to assess and identify flood hazards along the Oldman River and Willow Creek through the Town of Fort Macleod and the adjacent areas of the Municipal District of Willow Creek.

The Fort Macleod Flood Hazard Study is comprised of five major project components: 1) Survey and Base Data Collection; 2) Open Water Hydrology Assessment; 3) Open Water Hydraulic Modelling; 4) Open Water Flood Inundation Mapping; and 5) Design Flood Hazard Mapping.

NHC surveyed the channels and then used this data in combination with LiDAR and digital terrain model (DTM) provided by AEP in support of the modelling and mapping. Both the Oldman River and Willow Creek are regulated with numerous dams and diversions located upstream of the study. An open water hydrology assessment was conducted to determine the naturalized flows, that is the flow as if the channels were not regulated. Flood frequencies have been estimated on natural flows for the 2-, 5-, 10-, 20-, 35-, 50-, 75-, 100-, 200-, 350-, 500-, 750-, and 1000-year events. A HEC-RAS numerical model was developed and calibrated to support inundation mapping, river hazard assessment, and floodway determination. The mapping will guide future development along the study reaches and assist local officials with flood emergency response planning.