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Commercial Whitewater Rafting
Published in John R. Fletemeyer, Ivonne Schmid, Principles and Practices of Aquatic Law, 2018
Rapids are formed by the combination of gradient, obstacles, volume of water, and constriction. As water flows downhill, it gains momentum. When this volume of water goes over obstacles, such as boulders, it creates hydraulic features. Flow in natural rivers is characteristically nonuniform and unsteady.
Hydrodynamic considerations for improving the design/evaluation of over-topped bridge decks during extreme floods
Published in Structure and Infrastructure Engineering, 2023
Seyed Mehran Ahmadi, Mohammad Taghi Ahmadi
During a flood, which is a rapid water flow, the increased water level in the river, its relatively high velocity, and the application of hydrodynamic forces have detrimental effects on the bridges’ structures. So, comprehending complex turbulent flow and its hydrodynamic forces, particularly in extreme hydrological regimes, could mark an important step in evaluating bridge safety and the design of future bridges. In this context, a critical component of the bridge performance is its drag force. Determining drag forces is challenging when the bridge is inundated because of the complicated interaction between river flow and the bridge (Hamill, 1999).
A Lagrangian drifter for surveys of water surface roughness in streams
Published in Journal of Hydraulic Research, 2020
Christian Noss, Kaan Koca, Peggy Zinke, Pierre-Yves Henry, Christy Ushanth Navaratnam, Jochen Aberle, Andreas Lorke
Simple and fast methods for rapid large-scale surveying of hydrodynamics are required for investigating physical and biological processes in natural rivers and streams (Biggs, Nikora, & Snelder, 2005; Gurnell, Bertoldi, Tockner, Wharton, & Zolezzi, 2016; Marion et al., 2014). Measurements of the water surface roughness along river and stream reaches enable such simple and fast large-scale hydrodynamic surveys, provided that there are close relationships between water surface roughness and subsurface flow and turbulence. Several studies have provided information on the interaction between turbulence and the water surface; however, their results are limited to distinct flow conditions (Smolentsev & Miraghaie, 2005, high Froude-numbers), specific field conditions (Biron, Richer, Kirkbride, Roy, & Han, 2002, river confluence) or specific lab conditions (Dabiri, 2003, flow confluence; Savelsberg & Van De Water, 2009, grid-generated turbulence). The need for an in-depth understanding of the interactions between the flow and the free surface in natural flows was recently pointed out by Sukhodolov (2015). So far there is no unified classification nor ascertainment of water surface roughness (frequently denoted as waves, e.g. Leopold, 1969) in rivers and streams. Leopold (1969) distinguished four different classes of surface waves in rapids. Newson and Newson (2000) suggested eight different surface flow types (SFT) in response to physical habitat units. Although SFT have been frequently advocated as ecologically relevant units (e.g. Newson, Harper, Padmore, Kemp, & Vogel, 1998), mechanistic relationships between the SFT and subsurface flow conditions, riverbed roughness and stream ecology have been investigated only in a few studies (e.g. Noss, Bodmer, Koca, & Lorke, 2018; Reid & Thoms, 2008).