in a 1973 city of calgary flood plain management report by montreal engineering co. ltd., estimates of flood-frequency of the bow river upstream of the elbow river in calgary provided the following results: there is a 10-percent annual exceedance probability (aep) flood or a 10-year flood return period with a peak flow or flood discharge reaching ; there is a 4.5-percent annual exceedance probability (aep) flood or 22-year flood return period with a peak flow or flood discharge reaching ; there is a 1.4-percent annual exceedance probability (aep) flood or 70-year flood return period with a peak flow or flood discharge reaching ; there is a 0.7-percent annual exceedance probability (aep) flood or 150-year flood return period with a peak flow or flood discharge reaching .