Committee
Council Name: In-stream structures for
aquatic habitat restoration
Parent Committee/Council: Hydraulics and Waterways Council, Environmental Hydraulics Technical
Committee
Committee
Purpose:
The enhancement and restoration of streams to provide suitable habitat for macroinvertebrates, fish and vegetation (e.g., needed flow, water quality and food availability for the fish to reproduce and live at different life stages) is one of the most challenging tasks in river engineering. The presence of man made hydraulic structures like hydropower dams, weirs and other river training structures as well as poor watershed land management are, generally, negatively affecting the fish and plant/vegetation habitats in rivers. The diversity of biological species in a river correlates strongly with diversity of habitat parameters. Thus successful habitat restoration requires understanding of physical (flow, transport processes and their morphological impact) and biological processes in river systems.
In the case of fish, habitat structures such as rock/boulder clusters, rock weirs, sills, fish screens, fish guidance and exclusion devices, partially or fully submerged groyne fields, stone toes, etc are often built in rivers to provide feeding, spawning areas, facilitate resting, upstream/downstream migration or shelter from predators or environmental stressors (e.g., pollution), or to prevent fish from entering hazardous areas. The smaller velocities present inside or in the wakes of these structures provide cover and feeding opportunities for fish. Also the presence of these structures can induce considerable change in bed topography away from these structures by formation of local scour, pools and riffles which are beneficial for fish habitat.
Besides enhancing fish habitat some of these structures can play an important role in stabilizing eroding banks in incised channels. Incised sand-bed streams typically contain extremely degraded aquatic habitats as the effect of incisions is to sever the stream from the floodplain thus depriving the stream of carbon and nutrients. Aquatic habitats in unstable channels are typically of low quality due to the large variations of relevant hydraulic parameters, isolation of in-stream aquatic habitats from the floodplain, continuous shifting of bed material, increased turbidity levels, etc. Since the landscape can be significantly altered the potential of incision for degrading biotic integrity is very high. For instance, in the case of spur dikes their presence during low flow conditions creates ponding of water, a rise in the flow depth (thus their use for controlling navigation channel depths) and a decrease in the mean flow velocity in the channel reach which allows development of vegetation.
Another class of problems related to the presence of a certain class of in-stream structures (generally containing dead zones like groyne fields, side channels, bottom cavities) is related to the mass exchange between these structures and the main stream. The dispersion of pollution clouds due to accidental spills of dissolved matter in rivers and the effect of the presence of in stream structures (e.g., some of the pollutant can get trapped in these dead water zones) on the evolution of the pollutant cloud is a matter of great importance. Accurate prediction of the travel time, maximum concentration and spreading of a pollutant cloud requires accurate quantification of the exchange processes between the main channel and the dead water zones. The process can be inversed in the sense that the dead zone is polluted and the main stream is unpolluted. Other relevant situation is when the dead water zone is the source of a certain constituent (e.g., nutrients) whose spreading into the main stream is of importance. Related to the design of these large in-stream structures containing dead water zones the main requirements are: the formation of scour holes at the base of these structures should be maintained at a minimum to insure their long-term stability and the bio-diversity of flora and fauna due to the presence of the structure should not be diminished.
There is a need to develop a comprehensive interdisciplinary research plan using state-of-the-art experimental and numerical techniques that identify current challenges and areas where the effects of these structures on the aquatic habitat is not well understood; and ways toimprove and optimize the design of these structures. Finally, the findings of these investigations should be used toward proposing design variables and design criteria (standards) and recommendations that can be used by engineer practitioners toward conserving, restoring and enhancing aquatic habitat.
Committee
Objectives:
- Publication of a Special Issue in ASCE Journal of Hydraulic Engineering
- Organization of a Technical Session at the Joint ASCE-IAHR Conference in Vancouver 2009 focusing on employing state-of-the-art experimental and numerical techniques for the study of flow, erosion and mass exchange processes around structures used to enhance habitat in rivers.
Committee
Officers
Chair Name
Prof. George Constantinescu
Address: IIHR-Hydroscience and Engineering, The University of Iowa
Preferred E-mail sconstan@engineering.uiowa.edu
Preferred Fax Number 319 335 5238
Vice Chair Name
Prof. Panayiotis Diplas
Address: Department of Civil and Environmental Engineering, Virginia Tech
Preferred E-mail pdiplas@vt.edu
Secretary Name
Prof. Vincent Neary
Address Department of Civil and Environmental Engineering, Tenessee Tech University
Preferred E-mail Address vneary@tntech.edu
Preferred Fax Number 931 372 6239
Attach list of other committee members:
Prof.
Brian Bledsoe, Department of Civil Engineering,
Dr. David Crowder, Illinois State Water Survey (Illinois Department of Natural Resources), IL, crowderd@sws.uiuc.edu
Dr.
Andrew Goodwin, US Army Engineer Research and
Dr.
Robert McLaughlin, Department of Integrative Biology and Department of Zoology,
Dr. John Nestler, Environmental Modeling & System-wide Assessment Center, Engineer Research & Development Center, Vicksburg, MS , john.m.nestler@erdc.usace.army.mil
Prof.
Dan Orth, Dept. of Fisheries and Wildlife Sciences,
Committee
Mission and Focus:
One of the key missions of the Hydraulics and Waterways Council is to address environmental issues of increasing importance. Design of friendly fish passage structures and other in-stream structures to restore aquatic habitat as well as understanding the mass exchange processes around these structures (e.g., transport of nutrients between these structures and the main river reach or how pollutant dispersion is affected by the presence of these structures) is an environmental technical issue of increasing importance for river/coastal engineering. Eco-hydraulics provides the vital link between habitat and river engineering.
Milestone
dates for completion of planned committee activities:
Technical Sessions: September 2008
Special ASCE Journal of Hydraulic Engineering Issue: June 2007