• Energy Research

With the rapid development of wind power generation, many marine wind farms have been developed on the offshore intertidal sandbank (OIS) along the coastal regions of Jiangsu Province, China during the last decade. In order to quantitatively assess the stability of offshore wind turbines and their induced topographic changes on the OIS, a digital elevation model (DEM)-based analysis supported by satellite remote sensing is adopted in the present study. Taking the Liangsha OIS at the middle of Jiangsu coast, China as the research area, we first used an enhanced waterline method (EWM) to construct the 30 m resolution DEMs for the years 2014 and 2018 with the embedment of tidal creeks to effectively express the detailed characteristics of the micro-terrain. Then, a hypothetical sandbank surface discrimination method (HSSDM) was proposed. By comparing the height difference between the hypothetical and the real terrain surface during the operation period, the wind turbine-induced topographic change rate (TCR) was estimated from the DEM of 2018. The results show that 73.47% of the 49 wind turbines in the Liangsha OIS have an erosional/depositional balanced influence on the intertidal sand body, 8.16% show a weak depositional influence, and 18.36% lead to weak erosion. The average erosional depth, 58.6 cm, reached nearly 6% to 10% of the maximum possible erosion estimated by the hydrodynamic model. Furtherly, using two DEMs for the years 2014 and 2018, the topographic change depths at the location of wind turbines were calculated. By comparing the wind turbine-induced terrain change with the naturally erosional/depositional depths of the OIS, the average contribution rate caused by the wind turbines achieved 42.17%, which meant that the impact of wind turbines on terrain changes could not be ignored. This work shows the potential of utilizing satellite-based remote sensing to monitor topographic changes in the OIS and to assess the influence of morphological variations caused by wind turbines, which will be helpful for offshore wind farm planning and intertidal environment protection.

Offshore wind farms have developed rapidly in Jiangsu Province, China, over the last decade. The existence of offshore wind turbines will inevitably impact hydrological and sedimentary environments. In this paper, a digital elevation model (DEM) of the intertidal sandbank in southern Jiangsu Province from 2018 to 2020 was constructed based on the improved remote sensing waterline method. On this basis, the stability of the sandbank was analysed, and combined with the hypothetical sandbank surface discrimination method (HSSDM), the erosional/depositional influences of wind turbine construction on topography were quantitatively analysed. The results show that due to the frequent oscillations of the tidal channels, only 35.03% of the study area has a stable topography, and more than 90% of the wind turbines in all years have a balanced impact on the intensity of topographic change, and all see a small reduction in their impact in the following year. The remaining wind turbines with erosional/depositional impacts are mainly located in areas with unstable topography, but the overall impact of all wind turbines is balanced in 2018–2020. The impact of wind turbines on topography is both erosional and depositional, but the overall intensity of the impact is not significant. This study demonstrates the quantitative effects of wind turbine construction on topography and provides some help for wind turbine construction site selection and monitoring after turbine completion.