The paper presents the influence of subsidence and disappearance of organic moorsh soils on 4 longitudinal sub-irrigation ditch profiles located in Solec site (mazovian province, Piaseczno district, Góra Kalwaria community). The changes of the altitude of surface level and bottom of ditches were considered in years 1967-2013. Also the depths and slopes of the ditches were analysed. Based on performed research it can be concluded that the subsidence and disappearance of organic soils near the ditches closed to the river was observed in the range 80-120 cm in the years 1967-2013. It means that the average annual rate of soil surface lowering near the analysed 4 ditches was changing from 1,7 to 2,6 cm. It also caused the decrease of the depth and the changes of bottom slopes of considered ditches.