Quantifying the spatial pattern of urban expansion trends in the period 1987–2022 and identifying areas at risk of flooding due to the impact of urbanization in Lao Cai city

Analyzing urban expansion trends and its drivers is extremely important for sustainable urban development. However, in Vietnam, the urbanization process has been considered mainly in big cities, often ignoring the mountainous and border ones. The present study examined urban expansion and urbanization trends in different directions in Lao Cai city, northern Vietnam based on remote sensing and GIS data. After 35 years, the city's urban areas are mainly concentrated on the riverside and in the north-northwest direction (accounting for 27.95% of urban land area) due to the impact of the border gate economy. It is also for the reason that the intensity of urbanization (UII) in the range of 70–100% is mainly concentrated in the north-northwest region. With the urban intensity in 35 years reaching over 43%, Lao Cai is experiencing in a high rate of urbanization, but it has great potential flood risk. To determine flood risk in the study area based on natural and socio-economic factors, we used the Gauss process regression (GPR) model. However, due to the limitation of the GPR model, we combined GPR with Firefly algorithm (FA) to contribute to optimizing model performance. The results proved that the FA-GPR model is suitable for flood risk mapping in Lao Cai city. With R2 = 0.87, this work shows that the greater intensity of urbanization performs the greater flood risk. Therefore, for sustainable development, it is necessary to ensure harmony between economic goals and environmental protection goals. © 2022 Elsevier B.V.