Why Lincoln basements get wet
Clay holds water against the wall. The soil around most Lincoln homes is loess over clay. Wymore, the most common soil in Lancaster County, has a subsoil that is about 42 to 55 percent clay, according to USDA. Clay soaks up water but lets it drain out very slowly. So after a storm, water sits in the soil right next to your basement wall.
Spring saturation. USDA data shows the main clay soils here are often saturated within one to three feet of the surface in March and April. When the ground is that wet, water pushes on the basement wall from the outside. It comes in at cracks, at tie holes in poured walls, at mortar joints in block walls, and at the joint where the wall meets the floor.
Storm season. Lincoln gets about 29 inches of rain in a normal year, according to University of Nebraska climate records. May is the wettest month at about 4.9 inches, and June is close behind at about 4.5. Some months are far wetter. June 1967 brought almost 13 inches.
Creeks and low ground. The City of Lincoln lists 11 creeks and streams that can flood, including Salt Creek, Antelope Creek, Beal Slough and Deadman's Run. In May 2015, the city asked people in the North and South Bottoms to think about leaving their homes as water rose near the Salt Creek levee. Homes in low spots near a creek can see more water in the soil after big rains.
Clay that moves. The same clay swells when wet and shrinks when dry. It can open small cracks in a wall, and then the next storm uses them.
Older walls. About 1 in 8 Lincoln homes was built in 1939 or earlier. Many were built before drains around the footing and damp proofing on the wall were common.