Further downstream, Johnson Creek was more-or-less within its banks but ferocious. The stream is “flashy”. It rises and falls rapidly during storm events because most of its original riparian zones, which soaked up and released rainfall relatively slowly 200 years ago, have been converted to impermeable surfaces such as rooftops, parking lots, and paved roads. Consequently, a lot of the rain that falls rushes immediately into the creek. The creek rises and overtops its banks in the low spots, which are now covered with businesses and dwellings.
Restoring the riparian zones would mitigate the problem to some degree, but removing all of the buildings, streets, and other infrastructure along the creek to make way for marsh plants, shrubs, and trees would be incredibly expensive and would likely meet with fierce resistance from land owners, residents, and tax payers. During the Great Depression, the Works Progress Administration lined about 15 miles of the lower part of the creek with stone and straightened stream meanders. This created jobs but did not prevent floods; removing the meanders made the stream even flashier. In 2009, replacing bits of the riparian zone and encouraging water-retaining vegetation across the drainage basin may be the only approach with much hope of success. — Jer