In this context, suspended sediment (SS, fine-grained material suspended in water) pose additional hazards because they absorb and carry associated pollutants such as pesticides (Bhadha et al. Excessive sediment loads can have serious effects on water quality and water resources leading to silting of reservoirs, increased flood risk, damage to hydroelectric power plants or irrigation canals, a deterioration of water quality and higher treatment costs (Walling 2009). 2012), and in urbanized areas on the build-up and wash-off processes taking place on impervious areas or roads (Di Modugno et al. The intensity of the sediment transported to lowland rivers depends however on the soil type and channel erosion (Trimble 1997 Banasik et al. Similar findings on the impact of extreme events on the sediment yield contribution in the catchment have been also reported, among others, by Larson et al. According to USGS ( 2016), the sediment loads discharged from the catchment during one large flood event can account for more than half of the total load yielded throughout the whole year. For example, Edwards and Owens ( 1991) based on the analysis of more than 4000 rainfall events over 28 years have found that the biggest five events from all recorded events accounted for 66% of the total erosion. Depending on the catchment, the discharged sediment loads may vary substantially between dry and wet periods and between different flood events. (iii) Our findings acknowledge difficulties in describing SS routing through small reservoirs and indicate a lack of knowledge on the functioning of these reservoirs.īecause of heavy rainfall and intensive snowmelts, both the streamflow and the amount of transported sediment increase in local rivers (Hejduk et al. (ii) Thus, the parameter can be estimated from the sediment settling velocity and water flow velocity, but the correction factor must be applied. (i) The proposed SS routing model based on particle properties has been proven to accurately simulate SS in the reservoir outlet. This led to a high model performance for all events (Nash-Sutcliffe = 0.672 on average). Hence, there was a need to introduce a correction factor to accurately predict the effluent SS. The parameter calculated based on particle properties was about 10 times higher than the corresponding parameter optimized from recorded SS events. The performance of the proposed method was verified with the approach when the model parameter is estimated directly from recorded events. Suspended sediment samples at the reservoir inflow and outflow were taken manually during the passage of flood flows at irregular intervals. This model was tested on a small reservoir in Warsaw, Poland, with seven storm events. Hence, the model does not require a direct calibration with recorded data. This parameter is linked to the sediment settling velocity and water flow velocity. The SS routing through the reservoir is described following the single continuous stirred tank reactor concept with only one model parameter, the SS decay coefficient. A novel concept of suspended sediment (SS) routing through a small reservoir is proposed that relies on the particle properties in the reservoir inflow.