Browsing by Author "Cavus I."

Now showing 1 - 2 of 2

Changes in stream morphology protected by best management practices under effects of upstream disturbances
(2019-08-01) Cavus I.; Kalin L.; Kara F.
Stream channels are usually more stable in forested watersheds. However, intensive land disturbances in forested watersheds may disrupt the balance between flow and sediment supply, and result in variations in stream morphology even in the presence of well-designed best management practices (BMPs). This study evaluated the impacts of upstream land disturbances on downstream stream morphology where streamside management zones (SMZs) were present in two small adjacent watersheds in Auburn, Alabama, USA. Field surveys including the measurements of channel cross sections at bankfull stage were conducted at 12 survey sites over an 18-month period. Both in-stream sediment deposition and erosion were observed downstream of the disturbed areas in the study watersheds. As a result, channel cross sections exhibited very dynamic patterns changing frequently over short time periods. Overall, the dominant process was in-stream deposition in both watersheds due to large amount of sediment delivered from upstream-disturbed areas. In spite of the dynamic patterns of the channel cross sections in response to upstream disturbances, the commonly used parameters of Rosgen stream classification remained stable, suggesting that the upstream disturbances did not lead to changes in stream classification. In general, bank erosion was not observed. Therefore, it is likely that SMZs in each watershed were sufficient to stabilize streambanks by hindering in-stream bank erosion. Moreover, the poorly designed BMPs such as silt fences and straw bales near the disturbed area seemed insufficient to balance the variations in sediment supply under the impacts of upstream disturbances. This study emphasized that proper installation and continuous monitoring of BMPs should play a critical role on watershed management. It also indicated that watershed management should be handled using a holistic approach with well-distributed BMP applications within the entire watershed.
Impacts of urban headwater disturbances on downstream sediment loading where streamside management zones for forest harvesting activities are present downstream
(2017-12-01) Cavus I.; Kalin L.; Kara F.
Watershed disturbances caused by land use/land cover (LU/LC) change, intensive forestry practices, and other forms of watershed disturbance are known to negatively affect water quality, if best management practices (BMPs) are not present. Disturbances near or around headwaters where BMPs are absent or are inadequate may impact downstream water quality and stream ecology regardless of the presence of downstream BMPs. In this study, the recovery of two small forest-dominated watersheds (WW and EW) in Auburn, Alabama, USA, was monitored 6-years after a partial clearcut was done. The streamside management zone (SMZ) in WW was also partially harvested shortly after the partial clearcut to improve its sediment trapping effectiveness over the long-term. The hydrology and sediment transport in these watersheds were expected to stabilize over this period, however, new disturbances in the headwaters of both watersheds changed the watershed dynamics. Streamflow and sediment load were examined over a 15-month period from February 2014 to May 2015. The clearcut in WW and EW, and the partially harvested SMZ in WW seemed to have recovered; however, substantial amount of sediment load were measured across all monitoring sites in both watersheds as a result of upstream disturbances. This study emphasizes the necessity of watershed management as a whole, and the importance of BMP applications within the entire watershed. It also highlights the fact that watershed management and BMP implementation is a dynamic process, thus, strategies and techniques need to be continuously adapted in response to environmental changes.