I’m Sakthi Kiran, a Scholar from SASTRA university. My current project is to model the flood in Cuddalore district, Tamil Nadu, South India.
While importing the LULC shapefile into HecRAS, it shows “there were no valid polygons in the target LULC shape file”
If you’re still looking for an answer: try checking/repairing the geometry validity.
e.g. if you have QGIS, try the “fix geometries” or v.clean processing algorithm.
Also, don’t try to import a layer with “rings” (holes in polygons), as it confuses HEC-RAS.