The influence of wetlands on basin hydrology and channel hydraulics has been investigated for a small Canadian basin using the MIKE 11/NAM model of the Danish Hydraulic Institute (DHI). The Black Creek basin has an area of 93.58 km(2), 15.6% of which consists of wetlands. The methodology involved long-term continuous simulation of the basin with and without the wetlands. The present analysis shows that on an annual basis, wetlands reduce the total runoff by less than 1% and increase the evapotranspiration by about the same amount. Overland flow decreases 21% and base flow increases by 15% due to wetland presence. Groundwater recharge also increases by 15%. During individual runoff events, wetlands reduce runoff by about 5% and 1% in terms of peak and volume, respectively. The 1: 100-year flood under current conditions would become a 1: 35-year flood if wetlands were removed. Wetlands can suppress the snow-melt-generated flood peaks by about 15-20% during spring freshet and summer floods by 1-5%. Wetlands also reduce the water level by 3-5 cm and 5-8 cm during spring freshet and summer storms respectively. Channel flow, water level, and velocity are influenced by the wetlands only during rare flood events. (C) 2016 American Society of Civil Engineers.