Adaption through Design Coastal Ecological Corridor as a Nature-based Defense to Tackle Rising Sea Level

Due to the lack of concentrate on ecology, land subsidence caused by rampant urbanization, and therefore the consequences of absolute lowland rise pose a direct threat to cities 1. This research aims to explore the design of coastal ecological corridors combining recreation and tourism in order to let it absorb the impact of sea-level rise and, at the same time, curtail the speed of land subsidence. This research is Design-driven research based on the world's largest estuary sediment island, Chongming Island, located at the mouth of the Yangtze in China. This research seeks to provide designers with design references for this type of project. The paper briefly introduces nature-based ecological corridors and integrated solutions in the construction of coastal resilience and analyzes changes in land use and landscape pattern on Chongming Island. This research will focus on coastal ecological corridors' connectivity, width, and composition. The outcome will be applied to coastal wetlands, coastal ecological network construction, etc., to reduce the threat of land subsidence and slow lowland rise, particularly the impact of coastal disasters, whereas improving citizens' psychological perception.

Introduction

Globally, the sea level has been rising for more than 100 years, and it is expected to rise faster in the foreseeable future 1. As the center of the Yangtze River Delta, Shanghai faces the problem of rising water levels and the problem of gradual sinking 2. As a significant ecological barrier for Shanghai's future development, Chongming Island has been increasing year by year through reclamation under the demand of rapid urbanization and land expansion. However, the area of arable land and water bodies has continued to decrease. In particular, the water body has the largest decline, which has intensified land subsidence on Chongming Island, increasing pressure on biodiversity protection and increasing pressure in the face of rising sea levels 3. The gray infrastructure built to "control" floods, especially in extreme weather conditions, has become increasingly ineffective. 4

Policy”Eco-Chongming”: Nature-based solutions in coastal protection

Studies have shown that solutions based on coastal nature can reduce the damage of floods and storms more effectively than gray infrastructure alone and are more resilient. Traditional, concrete-based coastal defence structures are not able to adapt to and compensate for sea-level rise and, therefore, need to be regularly maintained and reinforced. In addition, this structure often leads to unnecessary erosion of other sites. Ecological corridor is an attractive option for coastal protection:they reduce wave strength and protect the coast from erosion, thereby stabilizing the rising coastline. In contrast to concrete-based solutions, Ecological corridor can grow as sea-level rise or, if necessary, can be easily adapted(4). Broadly speaking, the coastal ecological corridor is composed of green, blue, and gray infrastructure. It will involve green roofs, rain gardens, sunken green spaces, permeable pavement design, and the transformation of buildings to natural environments. Therefore, with the "ecological Chongming" policy proposed, compared with the construction of hard dams, the construction of landscape ecological corridors has become a meaningful way to slow down the speed of land subsidence and absorb the impact of sea-level rise.

Broken landscape and tourism

Chongming Island has a flat terrain and fertile land. It is suitable for urban construction and farmland development. Frequent development and utilization activities result in the fragmentation of natural landscapes, diversification of artificial landscapes, and fragmentation of landscapes. This landscape made of fragments dispersed in the territory has proved to be an inefficient model 5. However, the tourist ecological corridor can make the system work properly as a whole by connecting the natural, social, and cultural areas by connecting different habitat patches in series Coasts.(Fig.2)

On the other hand, the coast is vital for tourism and entertainment. There is evidence that the development of natural assets, biodiversity protection, and disasters management can improve the competitiveness of tourist destinations, thereby promoting the positive correlation between tourism growth and economic expansion. Therefore, the splicing of landscape fragments for the purpose of tourism development enhances the coastal resilience of nature-based solutions 6.

Changes in the occupation and uses of the land

With the support of GIS, aerial photos in 2000 and 2020 were used to analyze the land-use changes in Chongming Island. In the past 20 years, the total area of the study area has increased year by year. The area of construction land, forest land, tidal flats, and unused land increased by 5.47%, 18.39%, 42.30%, and 203.74%, respectively; the area of cultivated land and water bodies decreased by -3.82% and -39.81%, respectively.

The changes between land-use types are mainly from tidal flats to agricultural land, breeding farms, green spaces, water bodies; agricultural land to aquaculture farms, residential land, green spaces; and water bodies to agricultural land, and aquaculture farms, and tidal flats(3).

In summary, Chongming Island is facing problems such as land subsidence and frequent floods and droughts due to the sharp decrease of the water body area, natural woodland and other natural areas, the increase of construction land area which occurred in the urban development process in the past two decades. Nature-based coastal protection and sustainable coastal landscape design pills need to be applied in ecological corridors.

Methodology

The methodology to approach this research proposal is a mixture of methods used to corroborate and validate the research.

1. Literature review:The selection of studies to be included in our review and the studying
2. Graphical analysis: redraw and remodel cases
3. Critical survey: investigation of qualitative aspects that define the identity of the place
4. Elaborate a replicable methodology to apply the study to other coastal area.

Good practice examples:

I would like to mention some projects that have developed these ideas. I have chosen threetypes of projects related to the topic:

• Landscape recovery projects installed “Sustainable Urban Drainage System(SuDS): The Ekostaden Augustenborg initiative, Sweden
• Spatial plans related with tourism or recreation : The case of Menorca, The living breakwaters(Fig.3)
• Design of ecological corridor:Tomar Cultural Greenway(Portugal)

Most of them have been recognised with national and international awards which show the interest of their methodologies and proposals.