Effects of self-regulation mechanisms in vegetated channels on hydraulic resistance

Abstract

The aim of this thesis is to analyse the effects of self-regulation mechanisms in open channels with vegetated bed on hydraulic resistance, particularly bed slope effects. In order to examine them, laboratory experiments are carried out with artificial roughness. The self-regulation mechanisms investigated are: mean water depth, flow penetration depth and canopy height, as well as the applicability of Grishanin’s equation to open channels with vegetated bed. The first step is to perform this investigation is a preliminary analysis of the flume and its working conditions. Specific trials such as calibration of the flume with and without roughness elements and acoustic velocity measurements are performed. The results obtained are based on data collected from two types of experiments: hydraulic resistance and flow penetration. The experiments are performed using one type of roughness and density. This is tested for five different slopes 1in: 333, 500, 750, 1000, 2000 and six different flow rates: 10, 15, 20, 25, 30, 35 l/s, which is a total of thirty flow conditions. The laboratory experiments are performed in a 12.5m tilting flume with all the bed covered with roughness. The consistence of Grishanin’s equation fails for this setup, not being applicable. Therefore more research with a wider range of conditions might be performed. Moreover, it is found that might be different calibration line for low and high flow rates. There is also a different trend of the parameters analysed for steep slopes such as 1 in: 333, 500 and flatter slopes such as 1 in: 750, 1000, 2000. This thesis enables to know some of the effects of submerged vegetation in rivers and also how to relate them with its ecosystem in order to be able to model and predict water quality improvements.