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Half the population of China live in coastal zones where 70% of large cities are also located. Intensive human activities pose significant environmental and ecological hazards to these cities that are already vulnerable to natural hazards and climate change. The sustainable development of coastal cities is thus both a national and international issue. Rongcheng is a typical coastal city in east China. It is a national marine ranch demonstration area that is subjected to multi-stressors from human activities and climate change. The dominant economic sectors include aquaculture and fisheries, agriculture, shipping and tourism. A multitude of resulting pressures come mainly from intensified human activities, such as intensive aquaculture, overfishing, industrial pollutants, agricultural runoff, land reclamation and port expansion. In addition, Rongcheng is also facing exogenic pressures from extreme climate events such as intensified storms, storm surges, droughts and sea ice. A growing awareness of these problems brought together a trans-disciplinary group from local government, research institutions, local practitioners and coastal representatives to jointly explore and co-design adaptive coastal management options. In this transdisciplinary study, a social-ecological analysis based on a combination of the Systems Approach Framework and the Drivers-Pressures-States-Impacts-Responses framework was used to analyze and formulate an adaptive management plan for the sustainability of Rongcheng. More than 40 stakeholders including government, companies, civil society and institutions participated in the study through questionnaires and on-site meetings. A statistical analysis of the results identified urgent issues impeding the sustainable development of Rongcheng. The issues identified were poorly regulated aquaculture, loss of shoreline, and the decline of seagrass and cultural heritage.The study identified management options and measures, some of which were adopted by the local government in a co-designed management plan. The measures included upgrading of aquaculture industry, habitat conservation and restoration, and the development of cultural tourism. Another outcome was the increased knowledge exchange between stakeholders to inform management, policy, and decision making, as well as raised awareness of vulnerability to natural hazards and climate change. The success of this case study provides a reference for the adaptive management of other coastal cities and their sustainable development in a changing climate. info:eu-repo/semantics/publishedVersion

Additional file 1: Fig. S1. Current velocity in 1–8th August (a, d), 11–13th August (b, e), and 14–21st August (c, f) for non-typhoon years (top panel) and 2019 (lower panel) in the Yellow-Bohai Sea. Fig. S2. Ekman Pump velocity in 1–8th August (a, d), 11–13th August (b, e) and 14–21st August (c, f) for non-typhoon years (top panel) and 2019 (lower panel) in the Yellow-Bohai Sea. Fig. S3. Sea Surface Temperature (SST) in 1–8th August (a, d), 11–13th August (b, e) and 14–21st August (c, f) for non-typhoon years (top panel) and 2019 (lower panel) in the Yellow-Bohai Sea. Fig. S4. Sea surface salinity during 1–8th August (a), 11–13th August (b) and 14–21st August (c) for 2019 as well as the difference (d) between the first and last period in the Yellow-Bohai Sea. Fig. S5. Difference of euphotic depth between 1–8th and 14–21st August in 2019 in the Yellow-Bohai Sea.

Current velocity profiles in combined wave-current flows are investigated on the basis of available laboratory and field data. From the laboratory measurements of Van Doorn's (1982) S10RAL, S20RAL, M10RAL and M20RAL, it is found that there exists a boundary interaction layer (which includes the wave boundary layer) where the current eddy viscosity ϵc is dominated by the wave motion inside the boundary interaction layer and then by the current upwards. Based on this finding, a new and simple model is developed to predict current velocity profiles in the presence of waves. The input parameters used in the model are wave height H, wave period T, water depth h, bed roughness Ks, and a reference current velocity u r . In comparison with the former models of Christoffersen and Jonsson (1985), Coffey and Nielsen (1986) and Sleath (1991), the present model provides a simple method to explicitly calculate the wave friction factor, current friction velocity and current velocities without laborious iterations involved. Another new aspect of the model is that calculation of current friction velocities and current velocity profiles is quite simple and can be carried out with a simple scientific calculator. Results from the model are sufficiently accurate for engineering purposes.