you can "burn in" your stream along the dem,
I usually using HEC-GeoHMS extension to do that
for building dem dont forget using hidrologically corrected dem tools to make a dem valid for flood plain simulation
You can try TOPO TO RASTER Tool in the ArcToolbox, this tool enabling us to include some dataset as the interpolation control live river layer, height point layer, break lines layer, etc
Hi ransara
Check this link, it may be able to answer your question?? there are other topics on the page which
may be of interest to you as well.
http://gis.stackexchange.com/questions/18595/burning-stream-network-into-dem-layer-using-arcgis-desktop
You can use Qgis for download Sentinel products, here the reference and the how to..pls check it and hope be helpful, regards.
https://youtu.be/fVS2Ls2bUbk