Hydraulic Diversity Research Articles

Relations between hydraulic characteristics of step-pool-system and benthos in the Gunbetsu River

Step-pool systems are popular existences in a mountain river, those are composed of the transverse lines of large cobbles across a stream. The purpose of this study is to apply step-pool systems to a fish-way. Present paper describes results of field survey for the Gunbetsu River to clarify relationships between the composition of benthos and microhabitat. From the results, followings were found: Hydraulic characteristics influences habitat segregation of benthos, and superior species depends on the flow velocity. Relatively, there are many species which prefer to inhabit with large flow velocity and also its number of individuals increase. Circular Arc-shaped rib which has hydraulic diversity is superior to Transverse ribs for benthos habitats, so it could be thought that Circular Arc-shaped rib can provide a good feeding place for fishes.

The application of a hydraulic biotope matrix to the assessment of available habitat: Potential application to IFRs and river health monitoring

In an attempt to meet the requirement of the new South African Water law a number of initiatives are under way to determine the flow requirements for our rivers. An essential component of this initiative is the determination of the influence of changing flows on instream habitat. Two components need to be assessed: change in the aerial extent of habitat and change in habitat diversity. This paper presents a technique that aims to address qualitative and quantitative changes in instream habitat in response to changing flow discharge. A hydraulic biotope classification based on a matrix of substrate and flow type has been developed by the authors in collaboration with stream ecologists. Hydraulic biotope diversity was studied in the Buffalo River, Eastern Cape province, and results show how the composition of hydraulic biotopes depends on both the channel morphology and the discharge. These findings complement parallel studies carried out by Padmore and Newson in the United Kingdom. The classification system promises to provide a useful way to describe discharge-related changes in habitat. Early research by Wadeson and Rowntree was based on point surveys and ignored the spatial distribution and aerial extent of hydraulic biotopes. King and Schael have developed a mapping technique to describe the distribution of hydraulic biotopes, but its application is limited by time and manpower requirements. This paper demonstrates a relatively simple field technique, which is under development, based on overhead photography. The technique allows a quantitative assessment of the changes in the aerial distribution of hydraulic biotopes in response to changes in discharge. The potential application of this technique to both IFR assessments and the River Health Programme is discussed.

A geomorphological framework for the assessment of instream flow requirements

As South African ecologists become increasingly aware of the possible long term impacts of river regulation schemes on channel structure and associated aquatic habitats, fluvial geomorphologists are being called upon to assist in recommending instream flow requirements for future river regulation schemes. In South Africa, the standard procedure for the assessment of Instream Flow Requirements (IFR) is the Building Block Methodology (BBM). Central to the BBM is the assumption that the flow regime can be divided into three groups of flow: the low flows, freshes and floods. Each group has a particular ecological (and geomorphological) significance. The IFR assessments are applied at selected sites, chosen to represent the river reaches downstream of the dam site. This paper presents a geomorphological framework developed as a component of the BBM. This framework recognises five important geomorphological issues which are addressed within an IFR exercise: (1) A general assessment is made of the catchment condition to determine the potential for morphological change within the river. (2) An evaluation of the geomorphological characteristics of the river network is carried out to aid the selection of IFR sites within representative reaches. (3) At each IFR site an assessment is made of the relationship between hydraulic diversity and discharge for the different morphological units present at the site. This assessment relates in particular to the low flow component of the BBM. (4) The freshes and floods required to maintain channel form and bed condition are determined at each IFR site. An assessment is also made of the likely pattern and direction of morphological change that are likely to result from the recommended flow regime. (5) In the case of interbasin transfers, an assessment should be made of the potential impact of transferred water on the receiving channel. To illustrate the practical application of the geomorphological framework to an IFR procedure, an example is given from a recently completed study carried out in the Tugela River in KwaZulu-Natal, commissioned by the Department of Water Affairs and Forestry. The underlying theoretical principles upon which decisions were made are outlined in this paper.

A geomorphological framework for the assessment of instream flow requirements

Abstract As South African ecologists become increasingly aware of the possible long term impacts of river regulation schemes on channel structure and associated aquatic habitats, fluvial geomorphologists are being called upon to assist in recommending instream flow requirements for future river regulation schemes. In South Africa, the standard procedure for the assessment of Instream Flow Requirements (IFR) is the Building Block Methodology (BBM). Central to the BBM is the assumption that the flow regime can be divided into three groups of flow: the low flows, freshes and floods. Each group has a particular ecological (and geomorphological) significance. The IFR assessment are applied at selected sites, chosen to represent the river reaches downstream of the dam site. This paper presents a geomorphological framework developed as a component of the BBM. This framework recognises five important geomorphological issues which are addressed within an IFR exercise: (1) A general assessment is made of the catchment condition to determine the potential for morphological change within the river. (2) An evaluation of the geomorphological characteristics of the river network is carried out to aid the selection of IFR sites within representative reaches. (3) At each IFR site an assessment is made of the relationship between hydraulic diversity and discharge for the different morphological units present at the site. This assessment relates in particular to the low flow component of the BBM. (4) The freshes and floods required to maintain channel form and bed condition are determined at each IFR site. An assessment is also made of the likely pattern and direction of morphological change that are likely to result from the recommended flow regime. (5) In the case of interbasin transfers, an assessment should be made of the potential impact of transferred water on the receiving channel. To illustrate the practical application of the geomorphological framework to an IFR procedure, an example is given from a recently completed study carried out in the Tugela River in KwaZulu-Natal, commissioned by the Department of Water Affairs and Forestry. The underlying theoretical principles upon which decisions were made are outlined in this paper.

ASSESSMENT OF RESTORED RWERINE HABITAT USING RCHARC1

ABSTRACT: The Riverine Community Habitat Assessment and Restoration Concept (RCHARC) was developed to integrate habitat enhancement into the stream restoration process. RCHARC assumes that aquatic habitat quality is closely related to hydraulic diversity based upon a “comparison standard” reach approach to stream restoration. A Beta test was performed by applying the RCHARC process to Rapid Creek in Rapid City, South Dakota. Standard and restored stream reaches were selected and data were collected. A comparison of field data and velocity‐depth distributions indicated that the restored stream closely replicated the standard reach. The RCHARC methodology has the potential to assess habitat quality for planned comparison reaches and indicate the level of success resulting from restoration.