Saccharum procerum

Saccharum procerum Roxb., Fl. Ind. 1: 243 1820. (syn: Erianthus procerus (Roxb.) Raizada; Ripidium procerum (Roxb.) Grassl);
.
Assam; Bangladesh; China South-Central; China Southeast; East Himalaya; Jawa; Myanmar; Nepal; Thailand; Tibet as per Catalogue of Life;
.
Nepal to S. China and Indo-China: Assam, Bangladesh, China South-Central, China Southeast, East Himalaya, Myanmar, Nepal, Thailand, Tibet as per POWO (Tripidium procerum (Roxb.) Welker, Voronts. & E.A.Kellogg, Taxon 68: 257 (2019));
.

Grass Id from BD _SM 615 : 6 posts by 3 authors.

Cortaderia selloana of poaceae ? 

I do not think it has distribution in the area as per Cortaderia selloana 

it seems saccharum sp.

Saccharum spontaneum L. ??

.

References:
POWO (Tripidium procerum (Roxb.) Welker, Voronts. & E.A.Kellogg, Taxon 68: 257 (2019)) Catalogue of Life  The Plant List Ver.1.1  WCSP  IPNI  GBIF (with type specimens) Flora of China  Annotated checklist of Flowering plants of Nepal  POWO  India Biodiversity Portal