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Urban waterlogging is a major natural disaster in the process of urbanization. It is of great significance to carry out the analysis of influencing factors and susceptibility assessment of urban waterlogging for related prevention and control. However, the relationship between urban waterlogging and different influencing factors is often complicated and nonlinear. Traditional regression analysis methods have shortcomings in dealing with high-dimensional nonlinear issues. Gradient Boosting Decision Tree (GBDT) is an excellent ensemble learning algorithm that is highly flexible and efficient, capable of handling complex non-linear relationships, and has achieved significant results in many fields. This paper proposed a technical framework for quantitative analysis and susceptibility assessment on influencing factors of urban waterlogging based on the GBDT in a case study in Guangzhou city, China. Main factors and indicators affecting urban waterlogging in terrain and topography, impervious surface, vegetation coverage, drainage facilities, rivers, etc., were selected for the GBDT. The results demonstrate that: (1) GBDT performs well, with an overall accuracy of 83.5% and a Kappa coefficient of 0.669. (2) Drainage density, impervious surface, and NDVI are the most important influencing factors resulting in rainstorm waterlogging, with a total contribution of 85.34%. (3) The overall distribution of urban waterlogging susceptibility shows a characteristic of “high in the southwest and low in the northeast”, in which the high-susceptibility areas are mainly distributed in Yuexiu District (34%), followed by Liwan District (22%) and Haizhu District (20%). To mitigate the impact of frequent urban flooding disasters, future measures should focus on strengthening drainage networks, such as optimizing impervious surface spatial patterns, controlling construction activities in high-risk areas, and preventing excessive development of green spaces.

Since the reform and opening up, China has achieved great progress in industrialization and urbanization. However, due to the long-term implementation of the economic development model of "emphasizing cities over township" and the urban-rural dual system, the gap between urban and rural development is constantly increasing, and the problems of land resource allocation and contradiction between man and land in rural areas have gradually emerged. Rural homestead is the main place where farmers live, with unique land use characteristics. The information such as the structure and utilization status of houses on it can clearly reflect the local rural economic situation and homestead problems. Therefore, understanding the characteristics and differences of rural homestead housing is of great significance to understand and grasp the situation and problems of rural development and promote the implementation of rural revitalization strategy. Based on the rural cadastral survey data of Guangdong Province and combined with GIS spatial analysis method, this paper analyzes the characteristics of rural homestead housing. The results show that: (1) The rural housing in the study area is relatively low, mainly with one floor, supplemented by two and three floors, mainly brick and mixed structure, supplemented by concrete structure, and there is a certain correlation between the number of floors and the spatial distribution of the structure. Among them, the proportions of one storey house, brick structure and mixed structure house are 59.42%, 37.71% and 42.60% respectively. (2) There are obvious regional differences in the number of floors and structural spatial distribution of rural homestead housing in the study area. Low-rise, brick and mixed structure houses are mainly distributed in remote areas such as northern and western Guangdong, and high-rise and concrete structure houses are mostly concentrated in the Pearl River Delta. (3) The vacancy and idleness of rural homestead housing in the study area are common. The average vacancy rate and idle rate are 6.75% and 5.66% respectively, and the rate of one househould with multiple houses reaches 23.88%. The phenomenon of rural hollowing is obvious, and 50.87% of the villages in districts and counties are above the moderate hollowing, mainly distributed in the fringe area of the Pearl River Delta and Meizhou in northern Guangdong. At the same time, there is a certain phenomenon that the average household homestead area exceeds the standard. (4) The characteristics of rural housing utilization in Guangdong Province are affected by factors such as policies, economy, transportation, physical geographical condition and local customs. And the influencing factors in different regions are different, such as the special folk customs have a greater impact on rural housing in eastern Guangdong, and the economic situations and urban siphon have a greater impact on the characteristics of rural housing in the edge of the Pearl River Delta. There are obvious spatial differences in the utilization of rural homestead housing in Guangdong Province, and there are many idle homestead resources. There is great potential for the optimization and adjustment of rural construction land for rural revitalization.