Investigation on Flood Resistance Characteristics of Waterfront Plants: A Case Study of Baxi Stream in Fujian Province, China

Urban waterfront green spaces are pivotal in maintaining urban-rural landscape patterns, enhancing habitats and biodiversity, modulating temperature and humidity, purifying air, mitigating noise, and improving the urban microclimate. They play a crucial role in regulating the urban ecological environment and enhancing natural environmental capacity. Several waterfront plants demonstrate a high adaptability to local hydrological and climatic conditions, and are resilient to drastic water level changes. Their roots can stabilize riverbanks or riverbeds during abnormal floods. However, there is a dearth of empirical research data on these native plants. This study focuses on the flood that occurred on June 13, 2022, in Baxi Stream, Yong'an City, Fujian Province, China, causing damage to revetments, sidewalks, plants, roads, and disrupting urban traffic. Utilizing this flood event as a case study, we collected terrain data via real-time kinematic (RTK) surveying and unmanned aerial vehicles (UAV). We examined flood traces on structures, buildings, and trees to determine the water level, water surface slope, and inundation depth of waterfront green space during the flood event. We also investigated several common invasive natural plants, including Gramineae, Cyperaceae, and Polygonaceae families, and artificially cultivated plants like Cannaceae. Using the plant type survey data, we calculated the shear stress and flow velocity during the flood event to comprehend the anti-flow characteristics of waterfront plants in the study area. Our findings revealed that naturally invasive Gramineous plants, such as Saccharum spontaneum L. and Phragmites australis, possess a high flood resilience, withstanding  mean flow velocity exceeding 5m/s. This study can provide a valuable reference for the selection of greening plants for waterfronts or plant engineering methods to safeguard waterfronts or riverbeds.