Rain needs a route that carries water away from the slab.
In Georgetown, heavy rain meets uneven ground, compacted travel paths, and rocky soil that does not always absorb water evenly. Runoff settles in low spots, follows the easiest path across the yard, and can travel beside a foundation or into a utility trench when the grade does not lead it away. Shallow fractures and irregular pockets in the ground can also send water along unexpected routes rather than letting it soak straight down.
A drainage layout starts with the source of the water and the elevation available for its outlet. Roof runoff, flow from higher adjacent ground, existing landscaping, and the path water already takes all affect where a drain line belongs. A line that is level, too small for the water feeding it, or ends where runoff returns toward the house does not solve the problem.
Keeping repeated runoff away from one side of a slab matters as well. Drainage that concentrates water beside the foundation leaves that side of the surrounding ground wetter than the rest, creating uneven moisture conditions around the structure.