It is commonly known that coastal vegetation dissipates energy and aids in
shoreline protection by damping incoming waves and depositing sediment in vegetated
regions. However, this critical role of vegetation to dampen wave forces is not fully
understood at present. A series of laboratory experiments were conducted in the Haynes
Coastal Laboratory and 2-D flume at Texas A&M University to examine different
vegetative scenarios and analyze the wave damping effects of incident wave height, stem
density, wave period, plant type, and water depth with respect to stem length.
In wetland regions vegetation is one of the main factors influencing hydraulic
roughness. Traditional open-channel flow equations, including the Manning and Darcy-
Weisbach friction factor approach, have been successfully applied to determine bottom
friction coefficients for flows in the presence of vegetation. There have been numerous
relationships derived relating the friction factor to different flow regime boundary layers to try and derive a wave friction factor for estimating energy dissipation due to bottom
bed roughness. The boundary layer problem is fairly complex, and studies relating the
wave friction factor to vegetation roughness elements are sparse. In this thesis the
friction factor is being applied to estimate the energy dissipation under waves due to
artificial vegetation. The friction factor is tuned to the laboratory experiments through
the use of the numerical model COULWAVE so that the pipe flow formulation can be
reasonably applied to wave problems. A numerical friction factor is found for each case
through an iterative process and empirical relationships are derived relating the friction
factor for submerged and emergent plant conditions to the Ursell number. These
relationships can be used to reasonably estimate a wave friction factor for practical
engineering purposes.
This thesis quantitatively analyzes wave damping due to the effects of wave
period, incident wave height, horizontal stem density, water depth relative to stem
length, and plant type for a 6 m plant bed length. A friction factor is then determined
numerically for each of the laboratory experiments, and a set of equations is derived for
predicting a roughness coefficient for vegetation densities ranging between 97 stems/m2
and 162 stems/m2.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2563 |
| Date | 15 May 2009 |
| Creators | Augustin, Lauren Nicole |
| Contributors | Irish, Jennifer, Lynett, Patrick |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Thesis, text |
| Format | electronic, application/pdf, born digital |
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