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Title: Flow-vegetation interactions : from the plant to the patch mosaic scale
Author: Biggs, Hamish
ISNI:       0000 0004 6346 3811
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 2017
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Aquatic plants occur in most river systems around the world and tend to reach their greatest abundance in stable, nutrient rich, lowland rivers. Determining the abundance of aquatic plants in river reaches and how they interact with flow is critical to understand their effects on river ecosystems and habitat. In this thesis new methods to survey aquatic macrophytes with unmanned aerial vehicles were developed. These methods were applied to surveys of 1,099 Ranunculus penicillatus patches, with distributions of parameters such as area, length and aspect ratio being reported. These data were then coupled with hydraulic measurements and showed that vegetation abundance corresponded to specific ranges of velocity, depth, slope, Froude number and stream power. At the plant or single patch scale, high resolution measurements of flow around R. penicillatus and the bryophyte Fontinalis antipyretica were undertaken in the field using stereoscopic particle image velocimetry (PIV) and acoustic Doppler velocimetry (ADV) systems. Both plant species caused substantial changes to mean velocities and turbulence in their wake, with the bryophyte causing a redistribution of energy to higher frequencies above the canopy. Complementary measurements such as plant geometry and biomechanics are also reported. The information in this thesis can improve scaling of future laboratory studies to more accurately represent field conditions. The aerial surveying and image analysis techniques can be used by regional councils, fishing trusts and other river managers to rapidly estimate vegetation abundance, surface area blockage factor and visualise flow through patch mosaics, enabling targeted river management strategies. The high resolution data on flow around individual patches can assist in the development of models of flow-vegetation interactions and provide reference data to test simulations. The technical and methodological developments in this thesis can also assist the design and execution of future studies by researchers seeking to pursue laboratory accuracy in the field.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Aquatic plants ; Water currents ; Environmental hydraulics