A master thesis from Aalborg University
Generering af syntetiske vandløbstværsnit til automatisering af habitatmodellering
[Generation of Synthetic Stream Cross Sections for Automation of Habitat Modelling]
Forfatter(e)
Semester
4. semester
Uddannelse
Udgivelsesår
2025
Afleveret
2025-06-03
Antal sider
159 pages
Abstract
Today, groundwater is overexploited in certain parts of Denmark, and at the same time, only 15% of Danish streams meet the environmental objectives set by the EU Water Framework Directive. The existing methods for determining the maximum acceptable reduction in streamflow due to water abstraction are considered to be inaccurate. Habitat modelling can be used as an alternative to current methods and is known to provide a more accurate determination of the acceptable minimum flow. However, habitat modelling is not commonly used in a Danish context, as the method often requires knowledge of the stream’s geometry in the form of cross sections. These cross sections are often unavailable and obtaining them is both time- and resource demanding. In this project, three models were developed: two for estimating the cross sectional area and one for assessing the depth distribution of the cross section. The first area model is an empirical model based on the Manning formula, while the second aims to improve the area prediction using a neural network. The Depth distribution of the cross section was likewise estimated using a neural network. Overall, these models demonstrated good accuracy in predicting both area and depth distribution. However, their performance was dependent on accurate estimation of the input parameters. The case study for this project is located in the Østerå stream, where surveyed cross sections were collected for the purpose of habitat modelling. The synthetically generated cross sections were compared with the surveyed ones in terms of performance within a habitat model. The synthetic cross sections were able to capture the relative change in habitat size and estimate an acceptable minimum flow consistent with the model using measured cross sections. It was concluded that for the casestudy the synthetic cross-sections generally overestimated the area, but were adequate for use in habitat modelling.
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