Abstarct: Check dams are small dams with very simple and relatively inexpensive structures and as they do not require any complicated technology or special materials for construction, they have many applications in flood and sediment control projects. In the present study, the effects of applying check dams in reducing peak discharges and increasing time to peak is investigated in Kan basin (approximately 215 km2 area) in north-west of Tehran. As this basin located near the Tehran and there are many recreational centers and Holy Shrines in this area, it has sensitive position. It is therefore necessary to take appropriate measures for reducing flood damages in this zone. The hydrologic and hydraulic modeling of the kan basin was performed using HEC-HMS software. Using hydrological modeling, the effects of check dam construction in mitigation of flood characteristics were evaluated in three scenarios. In the first scenario, the slope of upper sub-basins after check dam construction was considered to be reduced by half of the initial slope and the secondary slopes were reduced to a tenth and a hundredth of the initial slopes for the second and third scenarios, respectively. Results of hydrological modeling revealed that in the first scenario, check dams have no effects in reducing peak discharges and increasing time to peak. But in the second scenario, the peak discharges decreased by 0.88 percent and this reduction was between 3.86 to 10.61 percent in the third scenario. Also by using check dams, the time to peak of hydrographs were postponed to maximum of 10 minutes in second scenario and 10 to 50 minutes in the third scenario, which could be very effective by considering small time of basin concentration. In hydraulic modeling the effect of check dam construction was investigated by assuming that check dam reservoirs were empty of sediments. The slopes of sub-basins were divided in five ranges and the number of check dams was assumed 5,10,20,50,100,150 check dams in each range of slopes. In one case in each slope one sub-basin was modeled as the representative of its group and results showed that in this case by constructing 150 check dams, the least reduction of peak discharge in downstream outlet of soleghan with 50% slope was 65.7percent and maximum reduction in sangan sub-basin with 40% initial slope was 91.4 percent and the time to peak by constructing 150 check dams was postponed between 1 to 2 hour. In second case one sub-basin was modeled as witness sub-basin while all factors were fixed except slope factor. The result of this modeling showed that in this case reducing of peak discharge and increasing time to peak would be satisfactory and optimum. By comparing the results of two method of modeling it was shown from economic point of view the hydraulic modeling in is preferred and one can use watershed and management measures with check dams.