Abstract
Drought flow as the minimum flow rate required for restoration of the Mokgamcheon stream was calculated by the Storm Water Management Model (SWMM) V.5.0. The adequacy of drought flow to guarantee the minimum ecological environment was assessed using suitable low-flows not exceeding the maximum pollution concentration of the ecosystem calculated by Design FLOWs (DFLOW) V.4.1. Fish flows, which provide proper ecological habitat for fish, were calculated using Physical HABitat SIMulation (PHABSIM) V.1.5.2 to provide proper ecological habitat for target fishes such as Carassius auratus and Zacco platypus. The monthly expected instream flows were determined as the largest value between drought flow and fish flow. In most cases, instream flows were determined by drought flows exceeding fish flows that satisfy the condition of species habitat, but in the case of Carassius auratus, drought flows were less than fish flows in April, September, and October. Thus, structural measures for the supply of additional discharge were required. Instead, when natural environment-friendly instream structures, such as stepping stones were used, affordable ecological restoration that met the preferred conditions for discharge and depth of Carassius auratus was possible. The stepping stones were assessed using River2D V.0.95a to measure their effectiveness compared to other structural measures that would be costly and time-consuming to secure shortage of fish flow. Finally, the stability of the habitat was assessed through flood analysis; in case of a flood discharge of 5.2 m3/s obtained from time-series analysis, it was evaluated that the stability of habitats could be reasonable.
Highlights
River management projects all over the world, such as channel modifications and channel adjustments, typically focus on only hydraulic engineering practices that are designed to supply water and prevent flooding
Stream restoration attempts and related endeavors in the last two decades have focused on two related aspects: (1) rehabilitation of the ecological condition of urban streams that have been affected by ecological degradation and (2) preservation of integrity of the ecosystem and the environmental system
When river restoration is performed, ecological flow chosen for the main purpose, as well as drought flow, are secured and designed according to the restoration goal
Summary
River management projects all over the world, such as channel modifications and channel adjustments, typically focus on only hydraulic engineering practices that are designed to supply water and prevent flooding. The restoration of the ecosystem involves complex approaches that combine field survey, analysis, planning, construction, and maintenance of the instream habitat with its requirements of selected target species [8], such as total fish abundance, species richness, diversity, and equitability, which are crucial for habitat reach [9]. Such a process is only possible if the minimum amount of flow rate is first obtained from the ecological stream restoration project [10]. Despite all these diverse river restoration purposes, various measures have been established for stream restoration by giving priority to the restoration of aquatic organisms, securing sufficient flow rates, and improvement of water quality [13]
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