Complementary Effects of In-Stream Structures and Inset Floodplains on Solute Retention
Azinheira, David Lee
MetadataShow full item record
The pollution of streams and rivers is a growing concern, and environmental guidance increasingly suggests stream restoration to improve water quality. ï¿½Solute retention in off channel storage zones such as hyporheic zones and floodplains is typically necessary for significant reaction to occur. ï¿½Yet the effects of two common restoration techniques, in stream structures and inset floodplains, on solute retention have not been rigorously compared. ï¿½We used MIKE SHE to model hydraulics and solute transport in the channel, inset floodplain, and hyporheic zone of a 2nd order stream. ï¿½We varied hydraulic conditions (winter baseflow, summer baseflow, and storm flow), geology (hydraulic conductivity), and stream restoration design parameters (inset floodplain length, and presence of in stream structures). ï¿½In stream structures induced hyporheic exchange during summer baseflow with a low groundwater table (~20% of the year), while floodplains only retained solutes during storm flow conditions (~1% of the year). ï¿½Flow through the hyporheic zone increased linearly with hydraulic conductivity, while residence times decreased linearly. ï¿½Flow through inset floodplains and residence times in both the channel and floodplains increased non linearly with the fraction of bank with floodplains installed. ï¿½The fraction of stream flow that entered inset floodplains was one to three orders of magnitude higher than that through the hyporheic zone, while the residence time and mass storage in the hyporheic zone was one to five orders of magnitude larger than that in floodplain segments. ï¿½Our model results suggest that in stream structures and inset floodplains are complementary practices.
- Masters Theses