Rohan Benjankar

• PhD
• Associate Professor at Southern Illinois University Edwardsville

Dam operation impacts on stream hydraulics and ecological processes are well documented, but their effect depends on geographical regions and varies spatially and temporally. Many studies have quantified their effects on aquatic ecosystem based mostly on flow hydraulics overlooking stream water temperature and climatic conditions. Here, we used an...

This study investigates the effects of drawdown flushing in hydraulic structures on sediment transport and morphological changes within and around reservoirs. Utilizing the Smoothed Particle Hydrodynamics (SPH) method, the research focuses on local erosion induced by drawdown flushing and examines the interaction between water and sediment. To vali...

The cover image is based on the Research Article Collateral benefits: River flow normalization for endangered fish enabled riparian rejuvenation by Stewart B. Rood et al., https://doi.org/10.1002/rra.4255 . image

Floods are amongst the most destructive and costly natural disasters impacting communities around the globe. The severity and reoccurrence of flooding events have been more common in recent years as a result of the changing climate and urbanization. Best Management Practices (BMPs) are commonly used flood management techniques that aim to alleviate...

Like most rivers worldwide, the transboundary North American Kootenay/i River has experienced multiple impacts including watershed developments, river channelization, and floodplain clearing, draining, and diking. Construction of Libby Dam was authorized by the 1964 Columbia River Treaty (CRT) between the United States and Canada, and in 1975 began...

River damming has brought great benefits to flood mitigation, energy and food production, and will continue to play a significant role in global energy supply, particularly in Asia, Africa, and South America. However, dams have extensively altered global river dynamics, including riverine connectivity, hydrological, thermal, sediment and solute reg...

Flow and water surface elevation recession rate Regulated and unregulated flows Dam operation A B S T R A C T Fish can be stranded in pools during flow recessions that may occur naturally or as a result of dam operations. Past studies have recommended dam operation guidelines that only consider water surface elevation (WSE) recession rate to reduce...

Green roofs have been used to reduce rainfall runoff by altering hydrological processes through plant interception and retention as well as detention within the green roof system. Green roof media depth, substrate type, plant type and density, regional climatic conditions, rainfall patterns, and roof slope all impact runoff retention. To better und...

The importance of interactions among stream hydrology, morphology, and biology is well recognized in studies of stream ecosystems. However, when quantifying the impacts of altered flow on aquatic habitat, channel hydraulics and morphology are often considered either together, based on combined changes in topography and flow, or with variable flow o...

Native riparian forests provide the physical structure, nutrient inputs, and habitat elements necessary to support ecosystem function for many aquatic and terrestrial species. However, regeneration of these important ecotones is being negatively impacted by anthropogenic and climatic pressures, driving managers to consider creative ways to increase...

Climate change threatens biodiversity through global alteration of habitats, but efficient conservation responses are often hindered by imprecise downscaling of impacts. Besides thermal effects, warming also drives important ancillary environmental changes, such as when river hydrology evolves in response to climate forcing. Earlier snowmelt runoff...

The interaction between streamflow and bed-load sediment material plays a vital role in sediment transportation, and the modeling of hydrodynamic systems of coasts, oceans, and rivers should be considered in hydraulic and geotechnical studies. In this model, smoothed particle hydrodynamics (SPH) is used to simulate the dam-break wave propagation on...

The main objective of this study is to evaluate the performance of the integrated hydrological model, MIKE SHE in a small watershed to analyze the effect of two different precipitation sources on model outputs (groundwater elevation and surface water flows). The model was calibrated and validated with observed groundwater elevations and surface wat...

Studies have shown that salt concentrations are increasing in waterbodies such as lakes, rivers, wetlands, and streams in areas where deicers are commonly applied for winter road maintenance, resulting in degraded water quality. As the salt concentration varies spatially and temporally based on environmental and hydrological characteristics, we mon...

Quantifying geomorphic conditions that impact riverine ecosystems is critical in river management because of degraded riverine habitat, changing flow and thermal conditions, and increasing anthropogenic pressure. Geomorphic complexity at different scales directly impacts habitat heterogeneity and affects aquatic biodiversity resilience. Here we sho...

Human activities alter salt concentration of water sources such as lakes, ponds, wetlands and streams, which will have detrimental impacts on water quality and aquatic ecosystems. We developed electrical conductivity (EC)–based sensors to measure salt concentrations in water bodies. We calibrated and validated sensors using standard sodium chloride...

Native riparian vegetation communities have declined downstream of large water infrastructure like dams and diversions, owing to water management operations that prevent successful seedling colonization and recruitment. Altered timing and magnitude of reservoir releases to fulfill competing water demands often lead to reduced peak discharges and fl...

Riparian forest recovery was monitored over a 23 km study site that encountered a mixed low to moderate severity wildfire on the floodplain that was followed by a sequence of flows ranging from below bankfull to a 50-year flood on the regulated South Fork Boise River, Idaho, USA. The goals of the study were to examine the dominant mechanisms of pos...

Stream biophysical processes are commonly studied using multidimensional numerical modeling that quantifies flow hydraulics from which parameters such as habitat suitability, stream carrying capacity, and bed mobility are derived. These analyses would benefit from accurate high‐resolution stream bathymetries spanning tens of kilometers of channel,...

Management and conservation of freshwater habitat requires fine spatial resolution and watershed-scale and life-stage-specific methods due to complex linkages among land, climate, water uses, and aquatic organism necessities. In this study, we present a valley-scale microhabitat resolution, process-based bioenergetics approach that combines high-re...

Sustainable reservoir-river management requires balancing complex trade-offs and decision-making to support both human water demands and ecological function. Current numerical simulation and optimization algorithms can guide reservoir-river operations for optimal hydropower production, irrigation, nutrient management, and municipal consumption, yet...

Hydrological processes in mountainous settings depend on snow distribution, whose prediction accuracy is a function of model spatial scale. Although model accuracy is expected to improve with finer spatial resolution, an increase in resolution comes with modeling costs related to increased computational time and greater input data and parameter inf...

Advances in remote sensing coupled with numerical modeling allow us to build a “virtual ecohydraulics watershed” at the micro‐habitat scale. This approach is an integrated modeling framework with a cascade of models including physical (hydrologic, hydraulic and stream water temperature) and biological (fish habitat) modeling at a resolution and ext...

Advances in topobathymetric LiDARs could enable rapid surveys at sub‐meter resolution over entire stream networks. This is the first step to improving our knowledge of riverine systems, both their morphology and role in ecosystems. The Experimental Advanced Airborne Research LiDAR B (EAARL‐B) system is one such topobathymetric sensor, capable of ma...

Accurate snow accumulation and melt simulations are crucial for understanding and predicting hydrological dynamics in mountainous settings. As snow models require temporally varying meteorological inputs, time resolution of these inputs is likely to play an important role on the model accuracy. Since meteorological data at a fine temporal resolutio...

Regulated rivers below dams have traditionally been managed using a minimum instream flow to provide adequate aquatic habitat. However, dam management, in conjunction with changes in climate and land use, challenges downstream ecosystem functions that cannot be properly addressed by a simple minimum flow requirement. Depending upon the river system...

Freshwater systems are progressively becoming more stressed with increased human demands combined with expected trends in climate, which can threaten native biota and potentially destabilize the ecosystem. Numerical models allow water managers to evaluate the combined effects of climate and water management on the biogeochemical processes thereby i...

Stream water temperature plays a significant role in aquatic ecosystems where it controls many important biological and physical processes. Reliable estimates of water temperature at the daily time step are critical in managing water resources. We developed a parsimonious piecewise Bayesian model for estimating daily stream water temperatures that...

Understanding the role of stream hydrologic and morphologic variables on the selection of spawning sites by salmonid fishes at high resolution across broad scales is needed for effective habitat restoration and protection. Here we used remotely sensed meter-scale channel bathymetry for a 13.5km reach of Chinook salmon spawning stream in central Ida...

Within riparian landscapes, river flows and stages determine habitat gradients from less to more dynamic, and these support different plant species and their life history stages that are adapted to specific positions along these gradients. The gradients are characterized by physical processes that vary in magnitude and duration, and these shape the...

Canyon river systems are laterally constrained by steep walls, strath terraces, and bedrock intrusions; however, semialluvial reaches are nested within these environments as discontinuous floodplains along the river margins. These semialluvial floodplains provide an example of dynamic-equilibrium set within high-energy fluvial systems, marking area...

Digital elevation models (DEMs) of river channel bathymetries are developed by interpolating elevations between data collected at discrete points or along transects. The accuracy of interpolated bathymetries depends on measurement error, the density and distribution of point data, and the interpolation method. Whereas point measurement errors can b...

Studies of the effects of hydrodynamic model dimensionality on simulated flow properties and derived quantities such as aquatic habitat quality are limited. It is important to close this knowledge gap especially now that entire river networks can be mapped at the microhabitat scale due to the advent of point-cloud techniques. This study compares fl...

We developed a GIS-based multi-metric assessment tool using model simulated long-term vegetation data to assess changes in riparian ecosystems due to altered hydrologic regimes. This allowed us to estimate spatial changes in a riparian system over several decades at annual resolution, to study system trends through time, and the effect of multiple...

This chapter examines causal interactions between physical habitat and floodplain vegetation. The complex network of hierarchical relationships illustrates the understanding of riparian ecosystem functioning. The relationships between riparian vegetation and fluvial hydraulic processes are considered and used to build a conceptual dynamic floodplai...

Hydrological alteration caused by dam operation and river modification has changed the dynamics of riparian vegetation in most river floodplain systems. In this study, a dynamic vegetation model was used to analyze the change in floodplain area occupied by individual vegetation types and vegetation succession dynamics as consequences of river modif...

Overbank sedimentation is an important process in river floodplain ecosystems and is a component of the floodplain geomorphologic evolution. The impact of suspended sediment supply on floodplain processes is still unclear because sediment deposition can be influenced by many factors. We quantified the effect of sediment supply (suspended sediment)...

This study presented the results of an application of a floodplain dynamic model to the Nakdong River, South Korea. At the Nakdong River, high flows are reduced by dams and the river bed is degraded. Both changes contribute toward the same result: the floodplain is hydraulically disconnected from the main channel and the morphology of the river has...

The Kootenai River floodplain in Idaho, USA, is nearly disconnected from its main channel due to levee construction and the operation of Libby Dam since 1972. The decreases in flood frequency and magnitude combined with the river modification have changed the physical processes and the dynamics of floodplain vegetation. This research describes the...

Three different forms of the Kappa statistic were used to compare simu-lated and observed maps to assess the predictive capability of a dynamic vegetation model. Kappas were used to compare vegetation model performance considering both individual vegetation classes and merged vegetation phases. The overall Kappa increased slightly from 0.18 to 0.21...

Physical processes and riparian ecosystems on many floodplains around the world have been severely impacted by human activities. For example, an 80 km long reach of the Kootenai River floodplain in Idaho is completely disconnected from the channel because of levee construction and upstream dam operation. River channelization and reductions in flood...

The regulated hydrograph of the Kootenai River between Libby Dam and Kootenay Lake has altered the natural flow regime, resulting in a significant decrease in maximum flows (60% net reduction in median 1-day annual maximum, and 77%-84% net reductions in median monthly flows for the historic peak flow months of May and June, respectively). Other key...