The two-stage ditch is a river restoration technique that aims at improving the sediment regime and lateral channel connectivity by recreating a small floodplain alongside a stream reach. This study aimed to analyze the efficiency of a two-stage ditch in improving the stream sediment structure and functions under different hydrological conditions (baseflow, post-bankfull, post-flood). Stream sediments were collected in channel sections adjacent to the two-stage ditch, adjacent to a natural floodplain along channelized reaches without inundation areas. Grain sizes, organic matter content and phosphorous (P) fractions were analyzed along with functional parameters (benthic respiration rate and P adsorption capacity, EPC₀). The reach at the two-stage ditch showed no changes in sediment texture and stocks, while the floodplain reach showed higher fines and organic matter content under all hydrological conditions. The sediments in degraded reaches were more likely to be P sources, while they were more in equilibrium with the water column next to the natural floodplains and the two-stage ditch. Only functional parameters allowed for assessing the restoration effects on improving the sediment stability and functionality. Due to its sensitivity, the use of P adsorption capacity is recommended in future studies aiming at evaluating the response of river sediments to restoration measures under different hydrological conditions.

中文翻译：

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二级沟渠和天然漫滩对不同水文条件驱动下沉积过程的影响

两级沟渠是一种河流修复技术，旨在通过在河流河段旁重建一个小型洪泛区来改善沉积物状况和横向渠道连通性。本研究旨在分析两级沟渠在不同水文条件下（基流、泛滥后、洪水后）改善河流沉积物结构和功能的效率。溪流沉积物收集在与两级沟渠相邻的河道段中，与沿着没有淹没区的渠道化河段的天然洪泛区相邻。分析了颗粒大小、有机物含量和磷 (P) 部分以及功能参数（底栖呼吸速率和 P 吸附能力，EPC ₀）。两级沟河段的沉积物质地和储量没有变化，而漫滩河段在所有水文条件下都表现出较高的细粒和有机质含量。退化河段的沉积物更可能是P源，而它们更多地与天然漫滩和两级沟渠旁的水体处于平衡状态。只有功能参数允许评估恢复对改善沉积物稳定性和功能的影响。由于其敏感性，建议在未来的研究中使用 P 吸附能力，旨在评估河流沉积物在不同水文条件下对恢复措施的响应。