Process for patching canals and ditches with a non-sagging polyurethane composition

Seams are sealed and surface defects are repaired in a polyurethane/geotextile composite applied over concrete, an earthen canal or a ditch with a non-sagging polyurethane composition. This non-sagging polyurethane composition is a reaction product of a polyisocyanate, a high molecular weight polyhydroxyl compound, and a compound containing at least two amino groups. A low molecular weight diol or triol, a catalyst and a filler are optionally included in the polyurethane-forming reaction mixture.