River Restoration Research Articles

Statistically derived morphological signatures of large river channels extracted from topo‐bathymetric LiDAR data

AbstractWith the development of LiDAR technology and the availability of topo‐bathymetric data of high quality, new methods are emerging to describe and understand more accurately fluvial geomorphology. We explore the capacities of probability density functions (PDFs) of detrended dimensionless elevations extracted from digital elevation models (DEMs) to document channels morphology and configuration. These DEMs were obtained from a topo‐bathymetric LiDAR survey of 450 km performed on the middle and lower reaches of the largest river of France: the Loire River. The objective is to propose a thorough and complete method for PDF analysis in order to assess the vertical structuration of river reaches presenting various fluvial patterns. The analysis was conducted on the PDFs of active channel belt of four sites selected for the diversity of their morphological configurations (anabranching, braided, channelized and meandering). Results showed that PDFs appear to be specific of a reach and that they are useful for describing its vertical structure. The simplification with Gaussian mixture model (GMM) is effective in slicing PDF and the resulting Gaussians components are related to morphological units (MUs). The distance between Gaussian curves obtained using GMMs can be considered as an indicator of topo‐bathymetric connectivity between MUs (e.g., main and side channels) on sites presenting multichannel or channelized channel configurations. The study showed the high potential of PDF and GMM analysis in the field of fluvial geomorphology and suggests interesting developments for river management and restoration.

Exploring the Factors That Influence Stakeholder Participation in Decision-Making for the Moat System Restoration Project in Tianchang City, China.

The driving factors have a critical effect on shaping stakeholder behavior toward participating in decision-making for river restoration initiatives. The participation of stakeholders is a vital determinant for increasing public confidence in the government and enhancing the acceptance of government decisions. Conversely, insufficient stakeholder participation in decision-making may lead to resistance to decisions on river restoration projects. Thus, the primary purpose of this investigation is to shed light on the complex interactions between the various drivers that underpin stakeholder participation in the context of the Moat System Restoration Project (MSRP). The extended Theory of Planned Behavior (TPB) describes the relationships between seven drivers that have positively influenced stakeholder participation behaviors: stakeholder attitude, priority, risk perception, trust in government decisions, motivation, intention, and knowledge. The empirical underpinning of this research was obtained through a questionnaire survey conducted in Tianchang, China, encompassing a sample size of 473. The empirical findings discern that stakeholder attitudes vis-à-vis the MSRP favorably influence stakeholder participation behaviors. Additionally, stakeholder motivation and intention have been discerned as catalysts for heightened stakeholder participation behavior. These findings promise to furnish invaluable insights, benefit forthcoming river restoration initiatives, and equip decision-makers with a profound understanding of strategies to enhance stakeholder participation.

Assessment and Comprehensive Evaluation of Large-Scale Reclaimed Water Reuse for Urban River Restoration and Water Resource Management: A Case Study in China

Replenishing reclaimed water into urban rivers, which suffer from reduced flow and deteriorating water quality due to anthropogenic activities, presents an opportunity for water resource management and ecological restoration, while the effect and evaluation need to be considered. This study investigated the feasibility of large-scale reclaimed water reuse in urban rivers, focusing on water quality improvements and reuse scheme evaluation, utilizing modeling software to simulate the water quality after implementing the reclaimed water replenishment scheme. After seven days of reclaimed water replenishment simulated, the water quality in the receiving urban rivers exhibited substantial improvements to different extents, with some rivers showing a decrease of over 90% in chemical oxygen demand (CODMn), ammonia nitrogen (NH3-N), and total phosphorus (TP) concentrations. A comprehensive evaluation method using the physical element extension–analytic hierarchy process (AHP) evaluation model was developed to evaluate the feasibility and efficiency of the large-scale project of reclaimed water reuse in urban rivers. The overall score of the large-scale reclaimed water reuse scenario reaches 89, approaching Level I and indicating a highly scientific and reasonable plan. This study contributes to the field of urban river restoration and water resource management by demonstrating the potential for improving water quality in urban rivers through large-scale reclaimed water reuse. The innovative comprehensive evaluation method offers valuable insights for guiding the implementation of similar projects in other urban river systems, addressing water resource challenges, and promoting ecological restoration in urban areas.

Azudes along the Serpis River: Cultural Heritage, Obstacles and Contested Authority

Preserving cultural heritage and achieving the Sustainable Development Goal of protecting life below water do not always go hand in hand. The case of the Serpis River sheds light on the political, cultural and legal tensions that may arise when pursuing these two policy goals. To better understand these tensions, we propose acknowledging that rivers are complex natural-cultural systems imagined and shaped through various actors’ values, interests, practices and infrastructures (Boelens et al. 2016). River restoration initiatives generate divisions between actors and institutions with different ways of defining and valuing natural and cultural heritage.

Numerical investigation on the effect of flexible vegetation in open-channel flow incorporating FSI

ABSTRACT The understanding and studying of the vegetation effect on the natural water flows is an important objective in modern scientific research regarding river management and restoration, with high environmental impact. Vegetation in the open-channel flow significantly affects the velocity of flow. In the present study, influence of the flexible vegetation on the flow characteristics of open-channel flow was resolved numerically using computational fluid dynamics. For the numerical study of the open-channel flow with flexible vegetation, fluid–structure interaction (FSI) is used. The obtained results were then compared with the numerical results of rigid vegetation. The influence of different parameters such as depth of flow, flow velocity, slenderness ratio of vegetation and density of vegetation were studied. It was found that incorporation of FSI in the analysis is essential to accurately predict the flow characteristics. It was also found that the simulation using FSI is more critical in case of submerged vegetation in an open-channel flow for all flow velocities.

Drainage area is not enough: multivariate hydraulic geometry in the Southern Blue Ridge Mountains, U.S.A.

ABSTRACT Regional hydraulic geometry curves, which relate drainage area to channel morphology, are powerful tools for river restoration and watershed management. While there is a strong correlation between channel morphology and drainage area, the importance of watershed slope and relief on channel-forming flow, especially in mountainous regions, cannot be ignored. This research used single variable power functions along with multiple regression to determine which network- and or local-scale variables are influencing channel morphology in the Southern Blue Ridge Mountains. Within this region, watershed topography (i.e. relief and slope) and or local-scale characteristics (e.g. channel slope and sinuosity) are better predictors of channel morphology than drainage area. Additionally, the importance of local-scale characteristics in the multiple regression models provide strong evidence that site-specific conditions can be just as important as watershed characteristics in determining channel morphology. While multiple regression has been used to create hydraulic geometry equations in other regions, this is the first study that determined whether non-drainage area multiple regression models perform better than models that include drainage area. With the increasing ease with which network- and local-scale characteristics can be calculated, this research shows a clear need to incorporate additional network- and or site-specific characteristics into hydraulic geometry equations.

Monitoring the Efficiency of a Catchment Restoration to Further Reduce Nutrients and Sediment Input into a Eutrophic Lake

The restoration of eutrophic river and lake ecosystems is an important task that has been conducted in numerous ways and at many locations around the world. However, such improvements of water quality are often temporary, as such ecosystems are dynamic, and restoration measures must be reassessed and modified. The restored catchment of a shallow eutrophic lake, Lake Seeburg, in central Germany, was monitored over a 13-month period. The restoration of the inflowing river a decade earlier included riverbed prolongation, gradient reduction, and the construction of wetlands upstream, which reduced the sediment input and silting up of the lake. As nutrient fluxes in the tributaries were still high, these restoration measures seemed to be insufficiently effective. This study aimed to locate nutrient hotspots and quantify the nutrient balances of the catchment. Nitrogen and phosphorous concentrations, river discharge, hydrochemical parameters (pH, temperature, oxygen concentrations) and turbidity, as a proxy for suspended particulate matter (SPM), were monitored monthly. Our data show that the lake functions as a nitrogen sink, whereas the phosphorous fluxes follow a seasonal trend with the negative balance in winter turning into a positive balance in summer with the onset of cyanobacterial blooms. The release of phosphorous from the wetland throughout the year indicates supersaturation and thus a permanent input of phosphorous into the lake. Consequently, phosphorus loading in the lake is quite high, fostering eutrophication. Furthermore, the very low precipitation rates during the study highlighted that the lake was not only controlled by external nutrient loads but rather was sustained by high internal phosphorous loading. Consequently, the remediation action of creating the wetland to restore the sedimentation trap and nutrient accumulation capacity was not sufficient.

Deconstructing dams and disease: predictions for salmon disease risk following Klamath River dam removals

The health of fish populations and the river systems they inhabit have broad ecological, cultural, recreational, and economic relevance. This is exemplified by the iconic anadromous salmonid fishes native to the West Coast of North America. Salmon populations have been constrained since the mid nineteenth century by dam construction and water reallocation. In the Klamath River (Oregon and California, USA), a series of dams built in the early-mid 20th century cut the basin in two and blocked anadromous fish access to more than 600 river kilometers. This dramatic loss of habitat, coupled with infectious diseases and resulting epizootics, have impacted the wellbeing of these salmonid populations. In 2023-2024, the Klamath River will undergo the largest river restoration project in US history. Removal of the four lowermost dams will cause profound physical changes to the river, including flow, water temperature, and channel geomorphology. The dam removals will reconnect the lower and upper portions of the basin, and provide fish passage after a century of segregation. Reestablishment of upstream and downstream fish movements will also alter the occupancy and abundance of the salmonid hosts and their pathogens. The increased habitat availability and longer migration routes will increase duration of pathogen exposure and potential impacts on juvenile survival and adult pre-spawn mortality. However, restoration of more natural flow and sediment regimes will decrease overall fish disease risk by disrupting complex parasite life cycles. To better understand these multifarious, competing factors, we review the salmonid species in the Klamath River, and provide an overview of their historical pathogen challenges and associated diseases and use this as a framework to predict the effects of dam removals on disease dynamics. Our review and predictions are a synthesis of expertise from tribal biologists, fish health specialists and fish biologists, many of whom have lived and worked on the Klamath River for decades. We conclude with recommendations for expansion of current pathogen monitoring and research efforts to measure changes in host-pathogen dynamics basin-wide.

Methodology to evaluate the effectiveness of hydromorphological restoration of rivers in Romania

In the context of the requirements of the Water Framework Directive to reinstate a river’s good ecological status after being severely altered by human pressures, river restoration became a major topic in the last decade in the EU and the number of projects implemented especially on hydromorphology increased. However, it is still uncertain whether these restoration measures have positive cumulative effects, i.e. hydromorphological effectiveness, when compared to reference conditions and expectations of stakeholders, because of inconsistent methodologies. Therefore, the goal of our project is to develop a methodology to evaluate the hydromorphological effectiveness of river restoration, based on standardised indicators, at various spatial scales, appropriate for implemented measures and for restored river types, weighting the expectations of actors and adapted to case studies in Romania. This methodological protocol could become also a useful tool to create a strategy and make decisions in the practice of river restoration. Moreover, this kind of analysis could contribute to clarifying the issue of standards in environmental projects.

Enhancing climate-resilient urban river restoration: predictive modeling of geomorphic changes

Abstract Urbanization and climate change are two potent forces shaping the contemporary environment. Urban rivers, integral to city life, are profoundly affected by these dynamics. While restoration efforts have yielded promising results, a persistent challenge lies in the inadequate consideration of geomorphic processes and climate change impacts in restoration planning. This study addresses this critical gap by proposing a novel approach for designing stable urban river geometries in ungauged basins. Leveraging the Soil Conservation Service (SCS) method in conjunction with General Circulation Model (GCM) data, our research focuses on determining design discharge and channel stability. Our principal finding, based on the incorporation of parameters related to precipitation, runoff, and effective discharge, indicates a projected 35% increase in the width of stable urban rivers in the future. These results underscore the urgency of integrating climate change considerations into urban river restoration initiatives. Neglecting this imperative aspect risks the failure of restoration projects, particularly in addressing geomorphic challenges intensified by climate change. This research offers a valuable framework for future restoration efforts, ultimately contributing to the resilience and sustainability of urban river ecosystems.

Water quality deterioration remains a major stressor for macroinvertebrate, diatom and fish communities in German rivers

About 60 % of Europe's rivers fail to meet ecological quality standards derived from biological criteria. The causes are manifold, but recent reports suggest a dominant role of hydro-morphological and water quality-related stressors. Yet, in particular micropollutants and hydrological stressors often tend to be underrepresented in multiple-stressor studies. Using monitoring data from four Federal States in Germany, this study investigated the effects of 19 stressor variables from six stressor groups (nutrients, salt ions, dissolved oxygen/water temperature, mixture toxicity of 51 micropollutants, hydrological alteration and morphological habitat quality) on three biological assemblages (fishes, macroinvertebrates, benthic diatoms). Biological effects were analyzed for 35 community metrics and quantified using Random Forest (RF) analyses to put the stressor groups into a hierarchical context. To compare metric responses, metrics were grouped into categories reflecting important characteristics of biological communities, such as sensitivity, functional traits, diversity and community composition as well as composite indices that integrate several metrics into one single index (e.g., ecological quality class).Water quality-related stressors – but not micropollutants – turned out to dominate the responses of all assemblages. In contrast, the effects of hydro-morphological stressors were less pronounced and stronger for hydrological stressors than for morphological stressors. Explained variances of RF models ranged 23–64 % for macroinvertebrates, 16–40 % for benthic diatoms and 18–48 % for fishes. Despite a high variability of responses across assemblages and stressor groups, sensitivity metrics tended to reveal stronger responses to individual stressors and a higher explained variance in RF models than composite indices. The results of this study suggest that (physico-chemical) water quality deterioration continues to impact biological assemblages in many German rivers, despite the extensive progress in wastewater treatment during the past decades. To detect water quality deterioration, monitoring schemes need to target relevant physico-chemical stressors and micropollutants. Furthermore, monitoring needs to integrate measures of hydrological alteration (e.g., flow magnitude and dynamics). At present, hydro-morphological surveys rarely address the degree of hydrological alteration. In order to achieve a good ecological status, river restoration and management needs to address both water quality-related and hydro-morphological stressors. Restricting analyses to just one single organism group (e.g., macroinvertebrates) or only selected metrics (e.g., ecological quality class) may hamper stressor identification and its hierarchical classification and, thus may mislead river management.

Significant Dynamic Disturbance of Water Environment Quality in Urban Rivers Flowing through Industrial Areas

The urban water environment is seriously affected by human activities. Rivers in highly industrialized areas, which often carry various types of industrial pollutants, such as metals and nutrients, are especially affected. In this study, the water quality of the Pi River, an industrial base that flows through Chengdu, a large city in Southwest China, was tested for one year. Heavy metal concentrations in the water, sediment, and macrobenthic and algal communities in the river were examined. The water pollution index (WPI) and trophic level index (TLI) were employed to measure the water pollution degree and eutrophication status, respectively. The Shannon—Wiener index (H’) and Margalef’s index (dM) were determined to represent the diversity and richness of macroinvertebrates. The principal component analysis (PCA) was employed to define the main heavy metal influencing factors in the Pi River. Our study showed that the eutrophication status increased with spatial change, and the eutrophication status was the most serious in the downstream reach, which was moderately eutrophic. The water body of the Pi River was seriously polluted by heavy metals, and the content of chromium (Cr) in the sediment and cadmium (Cd) in the water/sediment was far beyond the prescribed limit. In addition, we found that Cd had a serious impact on both the benthic and algal communities, and the benthic community structure was completely changed, destroying the original aquatic environment. We explored the mechanisms of the influence of Cd on aquatic fauna, and this information is of great significance for the future conservation of industrial urban rivers. In this study, the spatial–temporal variations in water quality and aquatic communities revealed the pollution status of a river flowing through industrial areas, which provided a basis for future river conservation and restoration.

A habitat connectivity reality check for fish physical habitat model results and decision‐making for river restoration

Abstract Fish physical habitat models are a tool for guiding restoration efforts in lotic ecosystems, but often they overestimate restoration outcomes because currently they do not incorporate habitat connectivity. This persistent issue can, in extreme cases, result in little or no improvement to fish populations after the restoration, wasting valuable conservation resources. We present a case study where practitioners applied a fish habitat model for multiple life stages of gravel spawning fishes to a 52‐km stretch of the Iller River but did so at a microscale implementation by setting up a model based on cross sections with a maximum of 200 m distance from each other. This approach provided an opportunity to assess the connectivity of habitats for gravel spawning fishes, that is, European Grayling (Thymallus thymallus) and Common Nase (Chondrostoma nasus), integrating probabilities to find suitable habitats for all life‐history stages and seasonal movements. We used the assessed habitat estimates (availability of distinct habitat types within reaches defined by the 200 m cross sections) to calculate the minimum distance a fish would need to overcome to change from one habitat type into the other as it hypothetically ‘grew up’ from egg to full spawning adult. This approach can be interpreted as a life cycle habitat check as it considers all habitat types that are necessary to fulfil the life cycle of gravel spawning fishes including their size, distance and flow direction‐related orientation (e.g. larvae habitats only used when downstream of spawning areas). Our results show that the assumption of complete connectivity would require long movement distances for vulnerable life stages to find suitable habitat. This puts the high priority on the creation of migration corridors and passability of migration barriers in question. Without consideration of habitat types for all life stages of a species and their spatial context, restoration will not be successful. Shortly said: A perfect migration corridor does not necessarily provide habitat connectivity. We recommend the application of the habitat connectivity approach when predicting the effect of restoration measures and particularly setting the priority of measures for mitigation of fish migration.

Impact of Lateral Gap on Flow Distribution, Backwater Rise, and Turbulence Generated by a Logjam

AbstractLogjams may form at natural obstructions and are also used as nature‐based solutions for river restoration and natural flood management. Previous research has described backwater rise due to logjams that span the full channel cross‐section and logjams with a gap between the lower edge of the logjam and the bed. Logjams that fill the channel depth, but not its width, leaving a lateral gap between the logjam and the channel bank, are also common natural formations and the focus of this study. The flow distribution between the logjam and the lateral gap, backwater rise, and wake turbulence are key factors in determining the ecologic and flood risk impact of a logjam. Specifically, relative to a channel‐spanning logjam, the introduction of a lateral gap can reduce backwater rise and increase the potential for trapping particles, such as nutrients or microplastics, within the wake region, but may also promote erosion in the gap. The choice of logjam and gap widths can be used to maximize flow and habitat diversity in rivers, while reducing erosion risk. We present experimental results demonstrating that the flow distribution between the logjam and the lateral gap can be predicted by assuming equal resistance through the logjam and gap sections. Further, we show that backwater rise can be determined from the predicted discharge through the logjam using a momentum balance developed for channel‐spanning logjams. Finally, turbulence generated within the jam was observed directly downstream of the logjam, and, for the densities considered, increased with jam density.

New Technologies in Geo-Hazards Analysis, Hydrogeology and River Restoration

Strong societal pressures are now seeking to restore balance to environments that have been destabilized by many years of poor practices in valley bottoms, geological subsoil and slopes [...]

Lessons learned from community and citizen science monitoring on the Elwha River restoration project

Community and citizen science (CCS) projects – initiatives that involve public participation in scientific research – can both sustain and expand long-term monitoring of large dam removal projects. In this article, we discuss our perspectives on CCS associated with the Elwha River dam removals. We summarize how the public has been or could be involved in monitoring and distill lessons learned for other large dam removal projects. Much of the Elwha monitoring involved technical field work requiring training and incurring potential liability risks, guiding projects towards smaller-scale public involvement. Partnering with organizations that have capacity for volunteer management expanded CCS opportunities and provided logistical support to project managers committed to public engagement. We found that many projects engaged with students and/or with paid or unpaid interns; compensating participants in various ways can help to create reciprocal relationships that support long-term monitoring. In the future, other large dam removals could consider planning ahead for community involvement in dam removal monitoring to accommodate the technical and potentially hazardous nature of the work – broadening who may be able to participate. In addition, involving community members in setting research agendas could be an important first step in engaging them in long-term monitoring, in turn facilitating multi-generational research at the timescale of landscape-level changes. Finally, explicit relationship-building with Indigenous communities can enhance the benefits of community engagement in dam removal science for all involved.

Expansive, positive changes to fish habitat diversity following the formation of a valley plug in a degraded desert river

AbstractWidespread hydrologic alterations have simplified in‐stream habitats in rivers globally, driving population declines and extirpations of many native fishes. Here, we examine how rapid geomorphic change in a historically degraded desert river has influenced habitat diversification and ecosystem persistence. In 2010, a large reach of the degraded and simplified lower San Rafael River (SRR), Utah, was impacted by the formation of a valley plug and began to shift from a homogenous, single‐thread channel to a complex, multi‐threaded riverscape. We combined field measurements and drone‐collected imagery to document changes in fish habitat due to the valley plug. Our results demonstrate that in 2021, the affected reach was more diverse than any other stream reach along the SRR, containing 641% more diverse habitat (e.g., pools, riffles, and backwaters) than what was measured in 2015. The plug reach also retained water for periods beyond what was expected during seasonal drying, with the total extent of inundation within the riverscape increasing by over 2800%. Since the formation of the valley plug, riparian habitat has increased by 230% and channel networks have expanded to more than 50 distinct channels throughout the zone of influence. Our results provide evidence of successful self‐restoration in a formerly highly degraded reach of desert river, and encourage new methods of desert river restoration. We aim to inform the use of large‐scale, disruptive restoration actions like intentional channel occlusions, with the goal of mitigating the impacts of simplification and increasing habitat persistence in the face of exacerbated aridity in the desert Southwest.

Hybridity and Multiscale Compatibility in Landscape Infrastructure for Mountain River Restoration: A Pathway Toward Environmental and Socio-Ecological Sustainability

River rehabilitation has traditionally focused on hard-engineering projects, which often fail to address environmental protection concerns and social-ecological services in a larger territorial context. In particular, mountain rivers pose unique challenges due to their diverse hydrological and morphological conditions, which are often overlooked by traditional restoration methods. Consequently, water quality deteriorates and social-ecological imbalances arise. To address these challenges, we propose a holistic solution that integrates landscape infrastructure (LI), a soft-engineered biophysical structure and process. Our approach combines hydrological analysis, ecological sensitivity assessment, and ecological design solutions to develop an LI framework for the Xiaojiahe basin in the Chongqing Mountain range in southwest China. This framework emphasizes integration across the spatial scale of landscape networks and corridors. Our study reveals the existence of fragmented river systems and limited connectivity among green spaces in the research area. The adoption of a comprehensive Landscape Infrastructure (LI) framework facilitates the execution of culturally sensitive and practical design solutions for Mountain Urban River Restoration (MURR) at different levels. This approach reinstates the multifaceted environmental and socio-ecological benefits of the basin. We believe that our approach can be applied to other cases with similar contexts and challenges.

Effect of river restoration on spawning activity of Iberian barbel (Luciobarbus bocagei)

In fluvial systems, where aquatic organisms are limited to living within river networks, anthropogenic barriers can interrupt connectivity and contribute to habitat fragmentation. Habitat connectivity is particularly important for migratory fish that need to move considerable distances for spawning, rearing, and refuge areas. In order to support crucial stages in the native fish species’ life cycles, compensatory measures were established in the Vilariça River due to the construction of the Baixo Sabor Hydroelectric Scheme (BSHS). Thus, the purpose of this work is to evaluate if the implemented measures, such as habitat-enhancing weirs and a flow bypass system releasing water from the BSHS, improved the survival and reproduction of a native species, the Iberian barbel (Luciobarbus bocagei). The assessment included the calculation of the number of spawning individuals and the Weighted Usable Area (WUA) of spawning habitat. In addition, to assess spawning activity, a spawn-per-unit-effort (SPUE) methodology was developed. The results showed that migration and spawning of L. bocagei were improved by increased flow velocity from the bypass system. The installed weirs also contributed to spawning success because they allowed the establishment of resting and spawning areas that were essential during reproductive period. It was possible to estimate the maximum SPUE of 5.4 spawns per minute at the spawning grounds with a 20 m reach and the number of fish observed, which ranged between 251 and 800 per fieldwork at the spawning grounds and resting areas. Furthermore, the maximum WUA was estimated to be 1580 m2 for a discharge of 1 m3/s (between median and maximum flow for spawning season) at a 2 km reach of the Vilariça River. This work showed that the rehabilitation of a tributary of a fragmented river due to the construction of dams was a valid compensatory procedure because it allowed the migration and spawning of the fish.

Numerical and analytical flow models in ecological channels with interaction of vegetation and freshwater

Aquatic vegetation interferes with river hydrodynamics, thus affecting the mass transport and energy transfer in an ecosystem. The flow over submerged vegetation is characterized by a complex velocity profile and multiple turbulence structures, which have been usually simulated using cylinders or strips in previous studies. Because the simplified vegetation configuration may hide or amplify some physical processes found in natural conditions, we investigate the velocity distribution and turbulence structure in foliaged vegetation flows using both analytical and numerical approaches. The main innovations and findings can be summarized as follows: 1) numerical and analytical models adopted in this paper accurately simulate the flow velocity profile in vegetated channel; 2) the Karman constant is found to be unsuitable for complex vegetation morphologies, so we proposed adjusted coefficient; 3) an image processing method is adopted to quantify the vegetation morphology accurately; 4) the existing mixing-layer thickness formula is found to be unsuitable for vegetation with leaves, an improved formula is proposed showing high correlation coefficient (0.9562) between measured and predicted data; 5) to ensure applicability to larger-scale hydrodynamic simulations, an analytical expression of Manning’s coefficient is proposed based on an analytical multi-layer flow velocity model. These research findings can provide theoretical support for the design of vegetated river and ecological restoration.