A basement is really a depression in the earth. Basements usually have damp proofing on the outside, but that does not stop the three main sources of basement water: runoff, roof water and groundwater. In many places, basements are cuts in the side of a hill. If the ground surface does not slope down away from the house, rainwater hits the ground surface and runs downhill into the basement through cracks and joints in the wall, and particularly the wall/slab joint at the bottom of the wall.
Roof water from the drip edge lands on the ground adjacent to the basement and percolates down into the sandy or gravelly backfill. It then runs into the basement, again via cracks and joint at the bottom of the wall. Gutters can help limit this problem, but gutters do not work when they are full of leaves or ice, or ice dams make them slope backwards.
Groundwater knows no boundaries. In New Hampshire it usually is near the top of the bedrock surface. The groundwater table rises in the spring and/or fall. If it rises above the basement slab and the exterior perimeter drain is unsatisfactory, the basement floods from wall joint and floor cracks/joints.
So, how can you win? There is no one right answer, but several possible solutions for every situation. Give us a call to explore the solutions to your basement water problem. You may be surprised.