Before Rohnert Park was developed, most rainfall fell onto natural areas. The water soaked into the ground until it reached a saturation point, at which time it traveled, sometimes below the surface of the soil, sometimes in above-ground swales, via sheet flow, to the nearest creek or water body.
With urban development of the area, impervious surfaces were created. An impervious surface can be a constructed surface -- like paved roads, parking lots and rooftops -- or a natural surface compacted in some way so that the infiltration of surface water is impacted or prevented. Rain falling on impervious surfaces creates runoff that is sent through our storm water system of street gutters and storm drains, quickly to the nearest creek and downstream.
While our conventional storm water system of gutters, pipes and channels has done its job to protect properties and lives here in this urbanized area, it also has had replaced some of the beneficial functions of natural surfaces that protect environments and populated areas downstream, such as lessening the peak storm water level, slowing the velocity of water through the waterbodies, providing infiltration to groundwater, and filtering out pollutants.
The City’s Public Works Department maintains the City-owned portions of the storm water system, including gutters, inlets, catch basins, pipes and outfalls.
Sonoma Water manages most of the flood control channels that course through Rohnert Park. The channels in Rohnert Park are included in "Zone 1A" (Laguna de Santa Rosa - Mark West Creek watershed), one of nine geographical zones encompassing a major watershed. These flood control zones were established in 1958 as a means of financing the construction and maintenance of flood protection works within Sonoma County. Sonoma Water either owns in fee the rights-of-way for constructed flood control channels, or holds easements on them for maintenance. Maintenance of flood control channels and creek beds are under contractual agreement with Sonoma Water.