A recent report on the floods of 2011 says changes need to be made to ensure an event of that magnitude does not happen again.
Completed by the U.S. Army Corps of Engineers, the report focuses on events south of the border but contains recommendations that would impact both countries involved in the flooding along the Souris River such as changes to the agreement governing the body of water.
The report detailed many of the reasons behind the flood, noting that the snowpack in the Souris River Basin set the stage and the intense rain showers that hit the area in June further exacerbated the situation. In a span of just seven days in June, 119 millimetres of rain fell on Weyburn and another 80 millimetres hit the Estevan area.
Due in large part to the rainfall, the report noted that the Saskatchewan Watershed Authority had trouble attaining the target flows set out in their agreement at the Sherwood Crossing which caused them to unnecessarily use up flood control storage in Rafferty Dam and to a lesser extent in Alameda Dam. The authors did add that in fairness to the SWA, the troubles they had reaching the target were largely because of an extreme storage lag and “delay in timing of large magnitude peak flow caused by the filling of overbank storage between Rafferty Dam and the Sherwood Crossing.”
The 1989 agreement that governs the Souris was also described as ambiguous, noting it does not accommodate summer rainfall flooding and that the wording in parts of the agreement need to be clearer and the operating plan revised.
The recommendations set out in the report also focus on the need to amend the Souris agreement.
The authors note that a continuing review process should be established to discuss forecasting techniques and deficiencies. They suggest a thorough review of the operating plan should be undertaken and a policy established that would clear the way for periodic future reviews. It also called for Annex A of the agreement, the area which speaks to such matters such as target and peak flows, to be updated and rewritten so it is easier to understand and includes provisions for summer rainfall events.
The report calls for governments on both sides of the border to look at additional flood control storage possibilities within reservoirs located in the Souris Basin and also on Long Creek and the Des Lacs River as the 2011 floods revealed the impact of both rivers is underestimated in the current treaty.
There were also calls for more gauges in the basin, particularly in the upper part of the Souris which would provide better and more accurate information for officials, something that was an issue at times during the floods.