Siddharth Saksena

Virginia Tech | VT · Department of Civil and Environmental Engineering

River bathymetry, which is vital for accurate hydraulic modeling, is not readily available at large scales because of the logistical difficulties in field surveys and uncertainties associated with remote sensing techniques. Several studies have explored the potential of conceptual models and interpolation algorithms to estimate bathymetry. These mo...

Modeling and mapping of floods using one (1D) and two-dimensional (2D) models has resulted in significant progress in our understanding of river hydraulics and hydrology. The existing modeling approach can be improved further through a better understanding of the interactions between river hydrodynamics and subsurface processes. Saturated condition...

Recent unprecedented events have highlighted that the existing approach to managing flood risk is inadequate for complex urban systems because of its overreliance on simplistic methods at coarse‐resolution large scales, lack of model physicality using loose hydrologic‐hydraulic coupling, and absence of urban water infrastructure at large scales. Di...

Increasing frequency of extreme rainfall induced catastrophic urban flood events in recent decades demands proactive efforts to assess flood risk and vulnerability. Here, we develop an integrative framework for fine spatiotemporal scale assessment of urban flood response to historical and future projected changes in extreme precipitation. The frame...

Background Matrix type transdermal buprenorphine patches have not been investigated in horses and may provide an effective means of providing continuous pain control for extended period and eliminating venous catheterization. Objective Assessment of the physiological variables (heart rate, respiratory rate, body temperature) and thermal nociceptiv...

A bridge versus culvert hydraulics approach may be taken to estimate the headwater of larger-span (or equivalently short) culvert-like structures, and design manuals often argue that the former should be technically preferred. A laboratory study was undertaken to investigate short and long box culverts, including roughness effects, with special att...

The salinity of inland freshwaters is rising globally, particularly in human dominated landscapes that receive deicers in the winter. Here we show that the salinization of an urban stream in Northern Virginia (USA) can be linked to salt sources using stream water age as a master variable. Younger stream water is associated with either low salinity...

Objective This study investigated the performance among four cardiac output (CO) monitoring techniques in comparison with the reference method intermittent pulmonary artery thermodilution (iPATD) and their ability to diagnose fluid responsiveness (FR) during a modified passive leg raise (PLRM) maneuver in isoflurane-anesthetized dogs undergoing acu...

Numerous cardiac output (CO) technologies were developed to replace the ‘gold standard’ pulmonary artery thermodilution due to its invasiveness and the risks associated with it. Minimally invasive lithium dilution (LiD) shows excellent agreement with thermodilution and can be used as a reference standard in animals. This study evaluated CO via noni...

Objective: To compare cardiac output (CO) measurements by transesophageal echocardiography (TEECO) and esophageal Doppler monitor (EDMCO) with pulmonary artery thermodilution (PATDCO) in anesthetized dogs subjected to pharmacological interventions. The effect of treatments on EDM-derived indexes was also investigated. Animals: 6 healthy male dog...

In animals, invasive pulmonary artery thermodilution (PATD) is a gold standard for cardiac output (CO) monitoring, but it is impractical in clinical settings. This study evaluates the agreement between PATD and noninvasive electrical cardiometry (EC) for measuring CO and analyzes the other EC-derived hemodynamic variables in six healthy anesthetize...

Estimating uncertainty in flood model predictions is important for many applications, including risk assessment and flood forecasting. We focus on uncertainty in physics‐based urban flooding models. We consider the effects of the model's complexity and uncertainty in key input parameters. The effect of rainfall intensity on the uncertainty in water...

Objective: To investigate the relationship between invasively measured stroke volume (SV) and (1) esophageal Doppler-derived indices such as stroke distance (StrokeD), flow time corrected (FTc), stroke distance variation (SDV), and peak velocity variation (PVV); and (2) arterial load (AL) variables during evaluation of fluid responsiveness (FR) in...

Objective: To demonstrate if modified passive leg raise (PLRM) maneuver can be used for volumetric evaluation of fluid responsiveness (FR) by inducing cardiac output (CO) changes during experimental induction and correction of hypovolemia in healthy anesthetized dogs. The effects of PLRM on plethysmographic variability index (PVI) and pulse pressu...

Hydraulic relationships are important for water resource management, hazard prediction, and modelling. Since Leopold first identified power law expressions that could relate streamflow to top-width, depth, and velocity, hydrologists have been estimating ‘At-a-station Hydraulic Geometries’ (AHG) to describe average flow hydraulics. As the amount of...

Several studies have focused on the importance of river bathymetry (channel geometry) in hydrodynamic routing along individual reaches. However, its effect on other watershed processes such as infiltration and surface water (SW)‐groundwater (GW) interactions has not been explored across large river networks. Surface and sbsurface processes are inte...

OBJECTIVE To evaluate cardiac output (CO) measurements using transpulmonary ultrasound (TPUD) technology and compare results with those of the gold standard, pulmonary arterial catheter thermodilution (PACTD), in 6 healthy anesthetized pigs during acute hemodynamic changes caused by manipulation of the blood volume. ANIMALS 6 healthy male Landrace...

With increasing focus on large-scale planning and allocation of resources for protection against future flood risk, it is necessary to analyze and improve the deficiencies in the existing flood modeling approach through a better understanding of the interactions among overland flow, subsurface flow, and river hydrodynamics. Recent studies have show...

A digital map of the built environment is useful for a range of economic, emergency response, and urban planning exercises such as helping find places in app driven interfaces, helping emergency managers know what locations might be impacted by a flood or fire, and helping city planners proactively identify vulnerabilities and plan for how a city i...

The effect of spatial scale and resolution has been quantified individually for different hydrologic and hydraulic processes. However, the model structure and intrinsic resolution are seldom modified to accurately capture scale‐dependent physical processes. Although automated calibration methods exist for computationally expensive integrated models...

Sand dams, a water-harvesting structure employed by rural communities in drylands have an inconsistent record of effectiveness. While many sand dams are highly functioning, improper siting, siltation, seepage, and high rates of evaporation from shallow sand reservoirs inhibit the water storage capacity of some sand dams. This study examines large-s...

The present study investigated primarily the appropriate stone-sizing of on-grade riprap aprons, and more specifically whether the current INDOT design policy may be overly conservative especially within the context of smaller culverts. In the study, laboratory experiments were performed with two pipe diameters, D = 4.25 in (0.35 ft) and 5.75 in (0...

A sinking stream pirated water from a series of waterfalls in a small catchment underlain by buried karst in northern Indiana after a sinkhole was scoured and enlarged over the course of 2016. The catchment has historical significance to Indiana, and the current landowners wish to restore flow to the waterfalls. We address the following questions:...

Current INDOT policy requires that culvert-like structures with spans greater than 20 ft be treated for purposes of hydraulic analysis as a bridge, and hence mandates the use of software such as HEC-RAS for predicting the headwater, rather than the culvert-specific software, HY-8. In this context, culvert-like structures are assumed to have a stand...

Floodplain mapping using hydrodynamic models is difficult in data scarce regions. Additionally, using hydrodynamic models to map floodplain over large stream network can be computationally challenging. Some of these limitations of floodplain mapping using hydrodynamic modeling can be overcome by developing computationally efficient statistical meth...

Majority of the flood inundation maps in the United States are created using 1D steady-state hydraulic models that are unable to simulate the surface water-groundwater interactions within the floodplain that can play a major role in determining the water depth and extent of the flooding. Saturated conditions in subsurface and floodplain can lead to...

Hydraulic design and environmental permitting require the knowledge of ordinary high water marks (OHWMs) because they determine the federal jurisdictional limits over nontidal waters. The U.S. Army Corps of Engineers (USACE) uses OHWMs for regulation of the "Waters of the United States" as well as for authorizing activities such as stream restorati...

Hydraulic design and environmental permitting are heavily dependent upon Ordinary High Water Marks (OHWM) because they define the active river channel. The United States Army Corps of Engineers (USACE) use OHWM for regulation of the “Waters of the United States” as well as for flood and drought management. Current methods to determine OHWM are base...

Topography plays an important role in the accuracy of flood inundation maps. Most current flood inundation maps are created using topographic information derived from Light Detection and Ranging (LiDAR) data. Although LiDAR data are very accurate, handling of very high resolution Digital Elevation Models (DEMs) from LiDAR can be computationally cha...

Topography plays an important role in determining the accuracy of flood inundation maps. A lot of the current flood inundation maps are created using topographic information derived from Light Detection and Ranging (LiDAR) data. Although LiDAR data is very accurate, it is expensive, computationally time consuming and not available in several areas...