Field-based measurement of hydrodynamics associated with engineered in-channel structures: the example of fish pass assessment

摘要

The construction of fish passes has been a longstanding measure to improveriver ecosystem status by ensuring the passability of weirs, dams and other in-channel structures for migratory fish. Many fish passes have a low biologicaleffectiveness because of unsuitable hydrodynamic conditions hindering fish torapidly detect the pass entrance. There has been a need for techniques toquantify the hydrodynamics surrounding fish pass entrances in order to identifythose passes that require enhancement and to improve the design of newpasses. This PhD thesis presents the development of a methodology for therapid, spatially continuous quantification of near-pass hydrodynamics in thefield. The methodology involves moving-vessel Acoustic Doppler CurrentProfiler (ADCP) measurements in order to quantify the 3-dimensional watervelocity distribution around fish pass entrances. The approach presented in thisthesis is novel because it integrates a set of techniques to make ADCP datarobust against errors associated with the environmental conditions nearengineered in-channel structures. These techniques provide solutions to(i) ADCP compass errors from magnetic interference, (ii) bias in water velocitydata caused by spatial flow heterogeneity, (iii) the accurate ADCP positioning inlocales with constrained line of sight to navigation satellites, and (iv) theaccurate and cost-effective sensor deployment following pre-defined samplingstrategies. The effectiveness and transferability of the methodology wereevaluated at three fish pass sites covering conditions of low, medium and highdischarge. The methodology outputs enabled a detailed quantitativecharacterisation of the fish pass attraction flow and its interaction with otherhydrodynamic features. The outputs are suitable to formulate novel indicators ofhydrodynamic fish pass attractiveness and they revealed the need to refinetraditional fish pass design guidelines.