Flood impact on water quality of small urban streams.

Flood situation (August 2002) in small urban streams radically changed status of water ecosystem, which had been created naturally and anthropogenically for a long time. The aim of the after-flood research has been to record development of a creek recovery in positive as well as negative sense: recovery of benthic colonisation and reloading of contaminants (heavy metals) in bottom sediment. The Botic creek (its one section) was chosen as an experimental stream. This section of the creak is influenced by combine sewer system (two overflows - CSOs) as well as storm sewer system (one outlet - SSO). Heavy metals concentrations in water, sediment and body tissue of benthic organisms of the Botic creek and quality of benthic communities were monitored long term before flood. Comparison of results before and after flood can better assess impact of extreme water stage on a small stream.