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Analysis of the Effects on Harbour Porpoises from the Underwater Sound During Thec Onstruction of the Borssele and Gemini Offshore Wind Farms

C.A.F. de JongF.P.A. LamA.M. von Benda-BeckmannT.S. OudS.C.V. GeelhoedT. VallinaT. WilkesJ.A. BrinkkemperR.C. Snoek

出版	TNO, Defence, Safety & Security, 2022
URL	http://books.google.com.hk/books?id=ETaXzwEACAAJ&hl=&source=gbs_api

註釋Effects of underwater noise on marine mammals during the piling of foundations for offshore wind farms (platforms and wind turbines) are currently estimated on the basis of exceeding threshold values for the exposure of the animals to underwater noise. This is done through the Ecology and Cumulation Framework (KEC).This study, commissioned by the Wozep program of Rijkswaterstaat, provides more insight into the response of harbour porpoises to pile-driving noise and into the relationship between pile-driving noise and the behavioural response. Based on the data from acoustic monitoring during the construction of the Borssele wind farms in 2019 and 2020 and during the construction of the Gemini wind farms in 2015, it was investigated which acoustic metric (weighted or not weighted for the various species-specific frequency-dependent hearing sensitivity) best explains behavioural changes in the harbour porpoise. Statistical analysis of the detection of porpoise echolocation sounds (porpoise positive minutes measured by CPOD equipment) as a function of the distance from the pile, shows that porpoises are detected less often during pile driving at distances of at least 7 km near Borssele, where the pile-driving noise had to remain within a noise limit, and up to at least 15 km at Gemini, where no noise limit was yet applicable. These distances are considerably smaller than calculated (50% probabilityof disturbance at a distance of approximately 30 km) based on the current KEC methodology.The analysis of the detection of harbour porpoise echolocation sounds as a functionof unweighted and weighted single strike sound exposure level of the piling hits (SELSS) shows various threshold values above which harbour porpoises are detected less often. Due to the applied mitigation measures and masking by ambient noise, it was not possible to determine the SELSS values at Borssele over the same frequency bandwidth as at Gemini. Therefore, the dose-effect relationships are not comparable. The logical assumption that a measure weighted for the hearing sensitivity of animals gives a better prediction for the behavioural response than an unweighted measure is not immediately confirmed by the analysis of the measurement data from the Borssele and Gemini projects.The study also shows that there are problems with the practical implementation of frequency-weighted SELSS, due to the uncertainty in both modelling and measurement of the high-frequency components of pile-driving noise, where ambient noise masks high-frequency pile-driving noise.The measurements at Borssele, where pile-driving noise has been mitigated and where busy shipping results in a high level of background noise, show that it is not always clear whether pile-driving noise is the main source of disturbance.The analysis of the detection of harbor porpoise echolocation sounds as a function ofthe unweighted and weighted sound level (SPL) of the underwater sound at Borssele and Gemini shows a clear shows a clear decrease in detections with increasing SPL values. That suggests that SPL may be a more complete measure for predicting behavioral response than SELSS. However, predicting the total SPL as a result ofall sources requires more information and models than are available, which means that this measure is not yet directly applicable for effect studies.