Invasive aquatic species such as Hydrilla verticillata (hydrilla) have become a pervasive and
nearly ineradicable part of the waterways of the American south. Hydrilla is an aggressive
colonizer; grows rapidly and rapidly blocks flow areas, which greatly reduces the capacity of
water supply canals. Hydrilla grows up through the water column and is present throughout flow
zones that are typically assumed to be free flowing and without resistance, other than that
transmitted via the mechanics of a Newtonian fluid. Hydrilla is highly flexible and its
morphology in the flow field is dependent on many parameters, including flow, growth stage,
cross-section geometry and substrate.
Traditional methods of calculating canal flow capacities assume that resistance to flow originates
at the boundary of the channel. These methods typically attempt to account for vegetation by
increasing resistance coefficients, which are associated with the boundary of the canal.
A combination of field studies and experimentation in three separate laboratory channels was
used to characterize the behavior of hydrilla and its impacts on open-channel flow. This work
developed relationships for energy losses of flow within the vegetation, as well as velocity
gradients within the vegetation and through the vegetation water interface to the open water.
The information developed in this investigation was used to develop a model of the cross-section
of flow with vegetation growing in the center of the channel. The model is based on the Prandtlvon
Kármán universal-velocity-distribution law; and uses modifications to the method of
calculating the hydraulic radius, to account for the increased frictional elements and reduced flow areas in the canal cross-section. A simple function was developed to estimate the
remaining flow capacity in a canal as a function of the remaining unblocked area.
The Prandtl-von Kármán universal-velocity-distribution law, together with modifications to the
method for calculating the hydraulic radius, can improve estimates of the flow in channels
impacted by submerged aquatic vegetation. The effects of a broad range of parameters can thus
be represented by a relatively simple function, which was developed in this project.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2879 |
| Date | 15 May 2009 |
| Creators | Demich, Larry Ralph |
| Contributors | Fipps, Guy |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | electronic, application/pdf, born digital |
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