The same amount of water floods more than before. Rotten roads, dastardly development While Bolton says logging has a substantial but temporary impact, roads built to haul logs have a more malignant effect on floods because roads tend to be permanent. Roads cause soil compaction, and the culverts that funnel water beneath them focus the runoff in gullies. Traditionally, roads were sloped so water gathers on the uphill side, only to be drained through culverts, which cause great erosion. Some roads are now sloped so water spills directly onto the slope, Bolton says, reducing the gullying and improving infiltration into the soil.
New roads are one thing.
Large amounts of pavement speed runoff and hinder infiltration. The result is faster, higher floods downstream.