Physical habitat, eco-hydraulics and river design: a review and re-evaluation of some popular concepts and methods

Abstract

ABSTRACT1. Improved linkage between physical characteristics of rivers and biological performance or potential is a recurrent theme in contemporary river survey, management and design. This paper examines the degree to which flow biotopes and functional habitats may be differentiated with respect to physical habitat delimiters, i.e. flow depth, velocity and Froude number.2. Re-examination of published data demonstrates only very broad associations between biotopes, functional habitats and 'low', 'medium' and 'high' bands in the chosen physical habitat delimiter. The associations are also not consistent between different delimiters.3. Re-analysis is complicated by considerations of research design and methodology. Further studies are required with greater control on the circumstances of observation (particularly flow stage and seasonality), which explicitly control for variance within and between different river cases, and which adopt more consistent terminology.4. Field data for a single river reach at low and high flows indicate that use of the Froude number, in particular, requires careful interpretation. Very different velocity and depth combinations can exhibit similar Froude numbers. This may obscure important contrasts, such as those between channel margin and channel centreline environments.5. Field data also reveal that the flow characteristics of even basic (riffle or pool) units of channel morphology exhibit strong stage-dependence. There are also significant variations when channel margins are isolated from the definitions of the bedforms or analysis of the data. Current practice which seeks to simplify field survey to channel cross-section transects is therefore likely to be misleading.6. Given these difficulties, attempts to link biotopes with ecological response appear premature. Further research might, however, be directed to identifying possible associations between combinations of flow types and bedforms or functional habitats. In this sense, the biotope concept may be more profitably employed as one of several surrogate measures for potential biodiversity.

Influence of morphohydraulic habitat structure on invertebrate communities (Ephemeroptera, Plecoptera and Trichoptera)

“…These tasks lead to the cooperation of several branches of science such as fluvial geomorphology, ecology, zoology, botany, etc. Contribution of fluvial geomorphology represents understanding and analysis of processes which form the river channel and methods of assessment of physical habitats (Newson & Newson 2000;Newson 2002;Gordon et al 2004;Clifford et al 2006). It was recognised in stream ecology that the diversity of stream communities is directly influenced by the heterogeneity of abiotic environment (Hynes 1970).…”

Use of Ecohydraulic-Based Mesohabitat Classification and Fish Species Traits for Stream Restoration Design

“…Because projects commonly involve channel reconfigurations at the reach-scale, pool-riffle sequences become a key morphological structure for restoration design [2][3][4][5]19]. Success of restoration projects with habitat enhancement objectives requires mesohabitat units to be designed such that geomorphic and hydraulic principles are applied for long-term dynamic stability by self-regulating maintenance processes [32,80,81]. In addition, ecological success of projects may require more detailed information on species-habitat relationships for target species or biota assemblages during the pre-design process.…”

“…A trait-based analysis can be completed by specifically linking physical habitat structures with basic biological needs of stream organisms, and fully utilizing existing autecology information on organisms from the potential recolonization pool [20,[113][114][115][116][117][118]. Why an organism occupies a particular stream location at a given time is therefore influenced predominantly by specific channel morphologies and hydraulic conditions [77,80,88,[119][120][121][122][123][124]. Within specific channel morphologies and hydraulic conditions, each species has a unique relationship to the different characteristics of physical stream habitat in order to find the basic biological resources for survival, e.g., food, reproduction, and shelter.…”

“…Local hydraulics influence fish habitat use directly or indirectly based on various biological needs, such as food resources [209,214,215], predation cover [210,216], and spawning requirements [217]. These studies referenced above provide the ecohydraulics perspective for fish habitat use and application for restoration design [80,[218][219][220].…”

Wireless CDN video streaming architecture for IPTV

“…Despite the increasing interest in analysis on the mesohabitat scale and in mesohabitat characteristics, few studies have tested the reliability of mesohabitat classifications (Thomson et al, 2004;Clifford et al, 2006;Schwartz & Herricks, 2008) or have studied the spatial and temporal variability of mesohabitat characteristics (Hilderbrand et al, 1999;Trainor & Church, 2003). Methodological and theoretical problems related to the identification of mesohabitats and transferability among rivers still need to be solved (Clif-ford et al, 2006).…”