Hi there, geographic factors that contributed to the decline of sumer is that it was located on a flat plain that made in vunerable to attack. Flat land with poor drainage led to salinization from irrigation waters. Grain fields of one city-state bordered those of another, which caused territorial wars. fights over boundaries and water rights. the cities grew too fast. As the fields of Sumer grew saltier, harvests became smaller.There was a lack of natural barriers that could discourage attack. I hope these help. Basically all of these are above were on my notes from my test that were causes of the decline of sumer.
