The　modeling　of　transient　flow　in　unsaturated　soils　for　rainfall-induced　landslides　using　a　novel　spacetime　collocation　method　is　presented.　A　numerical　solution　obtained　in　the　spacetime　coordinate　system　is　approximated　by　superpositioning　Trefftz　basis　functions　satisfying　the　linearized　Richards　equation　for　collocation　points　on　the　spacetime　domain　boundary.　The　Gardner　exponential　model　is　adopted　to　derive　the　linearized　Richards　equation　to　describe　the　soil-water　characteristic　curve　in　unsaturated　soils.　To　deal　with　the　rainfall-induced　landslides,　the　infinite　slope　stability　analysis　coupled　with　the　proposed　meshless　method　with　the　consideration　of　the　fluctuation　of　time-dependent　matric　suction　is　developed.　The　proposed　method　is　validated　for　several　test　problems.　Application　examples　of　transient　modeling　of　flow　for　rainfall-induced　landslides　in　homogenous　unsaturated　soils　are　also　conducted.　Numerical　results　demonstrate　that　the　proposed　method　is　highly　accurate　to　deal　with　transient　flow　in　unsaturated　soils　for　rainfall-induced　landslides.　In　addition,　it　is　found　that　the　numerical　method　using　the　Richards　equation　with　the　Gardner　model　may　provide　a　promising　solution　for　different　soil　textures.