Manning’s roughness coefficient in small scale nature-like fish passages
(2022) In TVVR22/5007 VVRM05 20221Division of Water Resources Engineering
- Abstract
- Fishway construction remains a crucial measure in environmental adaption of flow barriers. A well-functioning fishway should be able to pass all naturally occurring species of fish and other aquatic fauna. A common approach when designing and dimensioning a nature-like fishway is to calculate flows with Manning’s equation but the selection and impact of Manning’s roughness coefficient lacks a robust scientific background. In this study, field-data from four different nature-like fishway passages are collected to evaluate roughness coefficients for 19 different cross-sections. The average roughness coefficient was M = 10.5, spanning from M = 3.7 to M = 20.7. The method of field measurement was compared to two other ways of estimating... (More)
- Fishway construction remains a crucial measure in environmental adaption of flow barriers. A well-functioning fishway should be able to pass all naturally occurring species of fish and other aquatic fauna. A common approach when designing and dimensioning a nature-like fishway is to calculate flows with Manning’s equation but the selection and impact of Manning’s roughness coefficient lacks a robust scientific background. In this study, field-data from four different nature-like fishway passages are collected to evaluate roughness coefficients for 19 different cross-sections. The average roughness coefficient was M = 10.5, spanning from M = 3.7 to M = 20.7. The method of field measurement was compared to two other ways of estimating roughness coefficients from (Cowan, 1956) and (DVWK, 2002). Limitations included measurement difficulties and assumptions of uniform flow for easier application of Manning’s equation. Based on the results, Manning’s roughness coefficient should be lowered from a typical design value of 15 to around 10 when designing small scale nature-like fishways or when estimating low-flow conditions in regular sized fishways. Future studies should seek to build data sets for greater varieties of fishways, evaluate the effect of varying flow within a fishway and thoroughly estimate the impact of perturbation rocks. (Less)
- Popular Abstract
- As demand for green energy, from hydropower among other sources, is ever increasing it is crucial that ecological and not only climate aspects are considered. For hydropower one of the most important measures is to ensure migration possibility for all naturally occurring species of fish. This is many times best obtained by installation of nature-like fish passages. One important step in fishway design is flow calculations and in this study roughness of small scale fishways has been evaluated to improve fishway design.
A fishway is a conduit that allows fish to pass obstructions in waterways, typically dam structures related to hydropower or irrigation. Historically, focus on species with higher economic interest such as salmon and... (More) - As demand for green energy, from hydropower among other sources, is ever increasing it is crucial that ecological and not only climate aspects are considered. For hydropower one of the most important measures is to ensure migration possibility for all naturally occurring species of fish. This is many times best obtained by installation of nature-like fish passages. One important step in fishway design is flow calculations and in this study roughness of small scale fishways has been evaluated to improve fishway design.
A fishway is a conduit that allows fish to pass obstructions in waterways, typically dam structures related to hydropower or irrigation. Historically, focus on species with higher economic interest such as salmon and trout and their upstream passage has led to inefficient passage for general migration of other fish species. Today, focus is put on nature-like fish passages that act like a small natural stream that is easier to pass for fish and that also creates important stream habitats.
When designing and dimensioning such fish passages, Manning’s equation is commonly applied to calculate flows, but values for Manning’s roughness coefficient and its relation do different design parameters is not well known. In this study, roughness coefficients were calculated based on data from fish passages to evaluate values currently applied in design. Methods for adjusting the roughness value based on parameters such as flow, channel geometry and perturbation rocks was also studied, along with two separate methods for roughness coefficient estimation.
It was found that for smaller fish passages, or low flow conditions, currently used roughness coefficients needs to be adjusted, for medium sized fish passages current values were verified by the study. Some of the other tested methods showed promise but need further evaluation before they can be applied. Generally, it was also noted that very precise roughness coefficient calculations are not necessarily the most efficient way of spending resources, with the many factor that affect a fish passage after installation monitoring also remains crucial in their prolonged usage. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9090268
- author
- Jaworowski, Aleksander LU
- supervisor
- organization
- course
- VVRM05 20221
- year
- 2022
- type
- H2 - Master's Degree (Two Years)
- subject
- keywords
- Manning’s coefficient, flow measurement, fish passage, fish migration, roughness coefficient
- publication/series
- TVVR22/5007
- report number
- 22/5007
- ISSN
- 1101-9824
- language
- English
- additional info
- Examiner: Rolf Larsson
- id
- 9090268
- date added to LUP
- 2022-07-11 14:44:02
- date last changed
- 2022-07-11 14:44:02
@misc{9090268,
abstract = {{Fishway construction remains a crucial measure in environmental adaption of flow barriers. A well-functioning fishway should be able to pass all naturally occurring species of fish and other aquatic fauna. A common approach when designing and dimensioning a nature-like fishway is to calculate flows with Manning’s equation but the selection and impact of Manning’s roughness coefficient lacks a robust scientific background. In this study, field-data from four different nature-like fishway passages are collected to evaluate roughness coefficients for 19 different cross-sections. The average roughness coefficient was M = 10.5, spanning from M = 3.7 to M = 20.7. The method of field measurement was compared to two other ways of estimating roughness coefficients from (Cowan, 1956) and (DVWK, 2002). Limitations included measurement difficulties and assumptions of uniform flow for easier application of Manning’s equation. Based on the results, Manning’s roughness coefficient should be lowered from a typical design value of 15 to around 10 when designing small scale nature-like fishways or when estimating low-flow conditions in regular sized fishways. Future studies should seek to build data sets for greater varieties of fishways, evaluate the effect of varying flow within a fishway and thoroughly estimate the impact of perturbation rocks.}},
author = {{Jaworowski, Aleksander}},
issn = {{1101-9824}},
language = {{eng}},
note = {{Student Paper}},
series = {{TVVR22/5007}},
title = {{Manning’s roughness coefficient in small scale nature-like fish passages}},
year = {{2022}},
}