The combination of GIS with fuzzy set theory and deterministic models is known as GIS Fuzzy Modelling (GISFM). GISFM was adopted for support sustainable land use planning. In particular GISFM is applied for solution of the problem of investment allocation into worse part of the land drainage systems located in the Saint-Petersburg suburbs. The missing data about loads on water bodies by agriculture waste products from land drainage system is calculated and mapped automatically by the use of the ecological model and software developed. Complex evaluations of land drainage plots are carried out by fuzzy model with the use of four criteria (technological, economical, ecological and social) for two special tasks: 1) ecological criterion is more important and 2) economical criterion is more significant. The results show the opportunity of plots ranging by criterion of fund efficiency. All results are provided by measure of mistrust, which was created by GISFM.