Sea level is rising and submerging coastlines adjacent to the po delta. why is the delta pro grading out into the adriatic sea/

There are two main reasons as to why the Po River delta prograding out in the Adriatic Sea even thought the coastlines are being flooded by the uprising sea level.
1. The Po River on it's way from the Western Alps to the Adriatic Sea gathers huge amounts of sand, rocks, organic material etc. and it is depositing all of that on the touch line with the Adriatic Sea.
2. The coastline of the Adriatic Sea, where the Po River makes it's delta, represents an area with very shallow waters, so all of the materials that the river brings with it, are very easily deposited, and are not dispersed or sinking down.