Riparian vegetation plays a fundamental role in alluvial channel evolution by modifying flow and sedimentation dynamics. To elucidate the roles of sediment supply, flow‐dependent transport capacity, and morphodynamic feedbacks on the evolution of emergent vegetation patches over a single hydrograph, we conducted two experiments with different reach‐scale sediment supplies: a high‐supply experiment (HSE) and low‐supply experiment (LSE). We measured flow velocities, bedload transport, and topographic changes around a full‐scale patch of live emergent willows in an outdoor laboratory flume. Erosion occurred in the patch‐adjacent channel areas irrespective of the sediment supply, whereas deposition within the patch interior was suppressed in the LSE and enhanced in the HSE. The magnitude of patch deposition in each experiment was controlled by the local sediment supply to the patch and local sediment mobility during each discharge in the hydrograph. The local sediment supply was affected by bed morphodynamics at the patch head, which modulated the reach‐scale sediment supply by redistributing the bedload in the channel. Sediment mobility within the patch was flow‐dependent and a function of velocity and turbulent kinetic energy. For different discharges, the velocity in the patch changed proportionally with the freestream velocity; however, the turbulent kinetic energy was more sensitive, being elevated compared with the freestream during high flows and inhibited at low flows. Therefore, deposition and erosion within vegetation patches are not simply functions of the reach‐scale sediment supply or patch flow characteristics, as is often assumed, but additionally depend on the local sediment supply to the patch interior.

Habitat suitability index (HSI) is a fundamental factor in ecological river-restoration projects for assessing fish habitat to create inhabited environment for aquatic organisms. An accurate estimation of HSI requires long-term-monitored data including flow velocity, water depth, and bed materials; however, this is not easy to collect, and the dataset comprises local characteristics. Therefore, it is difficult to present a generalized method of HSI estimation with limited local and temporal data. In this study, the probability distribution was applied for HSI estimation with limited data measured in the tributaries of Han and Geum Rivers in South Korea. Log-normal distributions were applied to the water depth and velocity data of aquatic habitat for Zacco platypus, and then the developed log-normal distributions were used as the HSI. The HSIs developed by applying the log-normal distribution were compared with the HSIs developed using the instream flow and aquatic system group (IFASG) method. By using the log-normal-distribution-based HSIs, the environmental flows estimated through the physical-habitat-assessment models based on instream flow incremental methodology were also compared with the IFASG-based results. The environmental flows were determined to be similar within an optimal range in both cases of the tributaries of Han and Geum Rivers.

Fluvial biological habitat types are classified using the diversity in physical characteristics of a water channel. Recent ecological management studies have highlighted the potential of underwater sound as a quantitative indicator of habitat characteristics. We investigate the relationship between underwater acoustic characteristics and hydraulic factors of 12 habitat types in the Namdae Stream in Yangyang, Korea, namely riffles, pools, and step riffle habitats. In the riffles and pools, the underwater sound levels were measured as sound pressure levels (SPLs). SPL(RMS) and 1/3 octave band have been measured in the frequency range between 8 Hz and 20 kHz. Among riffles, high SPL corresponded to the descending level of flow velocity. Pools generally had a low SPL. Low-frequency sound waves in the upper regions are better transmitted in the deeper water. To quantitatively analyze the water depth and flow velocity, we used a regression between the observed water depth, flow velocity, and acoustic SPL. The application of this study was certificated. The correlation coefficients between SPL and flow velocity/water depth revealed specific frequency bands with very strong positive correlations between SPL and flow rate in riffles and very strong negative correlations between SPL and pool water depth. Consequently, underwater sound can be used as an alternative for evaluating biological habitats.

In the past, urban floods were primarily caused by river overflow due to insufficient conveyance capacity and inadequate infrastructure. However, in recent years, domestic flooding resulting from unplanned urban development has been identified as a major cause. To defend against and prevent urban floods, effective monitoring of urban infrastructure is essential, along with real-time analysis of monitoring data. However, current standards and methodologies for implementing such monitoring systems are insufficient.This study aims to develop monitoring techniques for obtaining accurate flow data from key urban flood defense infrastructure and to establish methods for real-time evaluation of urban flow rates using data collected from various infrastructure components. The major urban flood defense infrastructure addressed in this study includes in-city elements, such as sewage pipes, rainwater pipes, sidewalks, underground reservoirs, and pump facilities, as well as out-of-city features like natural reservoirs. The experimental facility is designed to allow all infrastructure components to operate both organically and independently, depending on the experimental purpose. This study focuses on the construction and design of these facilities.The experimental facilities are broadly categorized into urban floodplains, underground infrastructure, and out-of-city infrastructure. The urban floodplain replicates in-city infrastructure with a width of 35 meters and a length of 25 meters. It includes classified rainwater pipes, sidewalks, and a surface area designed to incorporate Low-Impact Development (LID) techniques in future experiments. The underground infrastructure features a network of rainwater pipes, underground reservoirs, collection systems, and pumping stations, designed to handle a maximum flow of 2 m³/s. The entire site is equipped to apply various monitoring techniques, with the construction of the experimental facilities planned in three phases, to be completed by 2026. AcknowledgementsThis work was supported by Korea Environment Industry & Technology Institute(KEITI) through R&D program for innovative flood protection technologies against climate crisis, funded by Korea Ministry of Environment(MOE)(RS-2023-00218973)