We investigated the runoff properties of SS, TN, and TP in the Mimitori River and the Takizawa River streaming in agricultural areas in Iwate prefecture, Japan. Field observations provide that the following findings: 1) the concentrations of SS, TN, and TP increase in paddling and transplanting period in paddy fields, 2) TN and TP concentrations strongly correlate with SS, 3) the loads of SS and nutrients are much higher during rainfall time. To examine the possibility to control SS sorbing nutrients, we carried out experimental studies on the charging and flocculation of the suspended particles as well as the resuspension of flocculated sediments. The results clarified that the flocculation behaviors qualitatively follow the DLVO theory and the resuspension behaviors are similar to those of natural sediments. Finally, we suggest that increasing calcium ions over 2mM is effective to settle down the particles.