Abstract: Session D 10:50 am (Back to Session D)
Improving Hyporheic Flow in Restoration Design
Grant Ginn, PE
The importance of hyporheic zone in nutrient cycling, temperature moderation and critical habitat is well documented, however it is given only passing attention in the design of stream restoration. It is common to site the reconstruction of channel features such as riffles and pools and the installation of instream structures as factors that will result in improved hyporheic flow without serious consideration being given to how configuration and installation of these features will actually influence the hyporheic zone.
There are many potential deficiencies in restoration practices with respect to improvement of hyporheic exchange. Consideration needs to be given to substrate composition and porosity, occurrence and orientation of head potentials, topographic influences, and subsurface soils and groundwater levels. Without evaluating these factors restoration efforts may not produce the positive affects intended and, in many instances, may be detrimental to proper hyporheic flow.
This presentation will provide descriptions of how the design of instream structures and bed features can be modified to improve hyporheic exchange. Replacing standard boulder and log weirs with structured run and glides can reduce hyporheic short circuiting, extend head potentials over greater areas, and expand lateral zones of hyporheic flow. Structured run and glides can provide more nature inflow and outflow interfaces which provides critical habitat zones. Additionally, substrate augmentation and configuration can improve necessary subsurface conveyance and promote hyporheic exchange.