Suspended sediment transport during rainfall and snowmelt-rainfall floods in a small lowland catchment, Central Poland.

Abstract

AbstractData on suspended sediment transport and loads during rainfall floods and snowmelt-rainfall events in Zagożdżonka watershed, Poland, were analysed. The particle size composition of the material transported in the lowland river was evaluated based on a low-angle laser light scattering technique. Results showed the variability in suspended sediment transport during floods during the 2-year (199 and 2000) investigation. It seems that the time of flood occurrence was quite important. The first spring floods after winter provide much more material and have an influence on the amount of sediment transported in the subsequent floods. Almost all relations between discharge and suspended sediment concentration (including snowmelt floods) showed a clockwise hysteresis pattern. This type of relation was caused by early suspended sediment depletion (exhaustion effect). The suspended sediment loads were similar in 1999 and 2000 (68.6 and 57.4 tonnes, respectively). The grain size distribution did not vary much and the d50 ranged from 0.0455 to 0.1021 mm with an average of 0.0797 mm. An increase in d50 with increasing discharge was observed, but only for discharges <0.1 m3/second. Above this value, a high variability was observed, although this may have been caused by the settling tank not working properly. Further studies are needed to investigate suspended sediment transport during both low flow and floods, with special attention to snowmelt and snowmelt-rainfall events.