The morphological expression of rivers provides a primary medium for human understanding of river geomorphology and the transmission of geographical information. In an ever-changing environment, constantly updated river monitoring data and products offer considerable potential for an explicit expression of river morphological characteristics and associated processes. This paper reviewed the advances in river morphology expression and examines how the various approaches can be utilized to interpret changing geomorphic features of rivers. First, taking alluvial rivers as the research object, river morphology is classified into three types of expression data and four categories of expression models. Then, the limitations of current river morphology models, such as uncertainty, inconsistency, and poor joint application, are analyzed. Finally, four outlooks are offered for improving river morphology expression, including stimulating the expression of river morphology with big data of rivers, redefining different river types, promoting multidisciplinary and interdisciplinary integration, and serving scientific management and decision-making.

Adding new lines on the basis of the existing public transport network is an important way to improve public transport operation networks and the quality of urban public transport service. Aiming at the problem that existing routes are rarely considered in the previous research on public transportation network planning, a public transportation network optimization method based on an ant colony optimization (ACO) algorithm coupled with the existing routes is proposed. First, the actual road network and existing bus lines were abstracted with a graph data structure, and the integration with origin–destination passenger flow data was completed. Second, according to the ACO algorithm, combined with the existing line structure constraints and ant transfer rules at adjacent nodes, new bus-line planning was realized. Finally, according to the change of direct passenger flow in the entire network, the optimal bus-line network optimization scheme was determined. In the process of node transfer calculation, the algorithm adopts the Softmax strategy to realize path diversity and increase the path search range, while avoiding premature convergence and falling into local optimization. Moreover, the elite ant strategy increases the pheromone release on the current optimal path and accelerates the convergence of the algorithm. Based on existing road network and bus lines, the algorithm carries out new line planning, which increases the rationality and practical feasibility of the new bus-line structure.

The riverine ecosystem is reliant on freshwater; however, morphological changes and sediment load destabilize the natural river system which deteriorates the ecology and geomorphology of the river ecosystem. The Lower Indus River Estuary (LIRE) geomorphological response was synthesized using satellite imagery (1986–2020) and evaluated against the field measurements. The estuary sinuosity index has an increasing trend from 1.84 (1986) to 1.92 (2020) and the estuary water area is increased from 101.41 km2 (1986) to 110.24 km2 (2020). The sediment load investigation at Kotri barrage indicated that the median size of bed material samples during the low-flow period falls between 0.100 and 0.203 mm and the bed material after the high flow has clay and silt (<0.0623 mm) ranging from 17–95% of the total weight of samples. The vegetated land loss on the banks is positively correlated with the peak runoff at Kotri barrage (r2=0.92). The bank erosion was computed with high precision (r2=0.84) based on an improved connection of the coefficient of erodibility and excess shear stress technique. This study will be helpful for policymakers to estimate the ecological health of LIRE, and sediment fluxes play an essential role in the mega-delta system and coastal management.

Since 2007, Ulva prolifera disasters have occurred every year in the South Yellow Sea of China, the largest green tide disaster in the world. The inter-annual differences make monitoring and early warning for such disasters difficult. This study used remote sensing data (2015–2019) to determine its spatio-temporal variations in all life cycles. The results showed a lay effect between the NDVI-mean and the coverage area of U. prolifera. The spatio-temporal distribution of U. prolifera showed stages and regional differences. From late April to early May, U. prolifera first emerged near the Subei Shoal. After development in the middle of the Yellow Sea, U. prolifera broke out in the eastern sea area of Shandong and Jiangsu, declined in the Shandong sea area, and disappeared near Qingdao. The cycle lasted for approximately 90 days. The sea surface temperature was the necessary condition for the disaster, and the sea wind field was the main driving force for its horizontal drift. This study overcomes the poor timing and continuity of remote sensing data in the monitoring of U. prolifera. It provides a theoretical reference for forecasting the outbreak period of U. prolifera and can aid policy-makers to avert such disasters in advance.

Urbanisation is accompanied by drastic urban sprawl and populations gathering in cities. The new urban districts in China have gradually become the most effective form of built-up area expansion, but the corresponding human activities within these built-up areas have not increased at the same rate, which has led to the emergence of urbanisation-related problems, such as ghost cities. However, few studies have focused on the evolution of this inconsistency within a city, especially at multiple scales. Based on Landsat images and the Defense Meteorological Satellite Programme-Operational Linescan System (DMSP-OLS) data, our study calculated the barycentre, the agglomeration degree and the consistency index to quantitatively analyse the spatio-temporal consistency between built-up areas and human activities within a city from 1993 to 2013. A mainstream urban example in China, Zhengzhou, which accepted financial and policy support from the government and underwent rapid urbanisation, was chosen as a case study. The results of this study showed that (1) the consistency between built-up areas and human activities was characterised by an approximately S-shaped curve that divided the city’s development into three stages, namely, relative stability (1993–1998), rapid development exhibiting inconsistency (1998–2008) and the optimisation and matching of spatial factors (2008–2013); (2) the inconsistency stage had two diametrically opposed patterns: the increase in human activities lagged behind the expansion of built-up areas, and the opposite occurred in older areas, which resulted in the emergence of ghost cities in new districts and crowded populations in the old cities; and (3) the inconsistency stage occurs easily; thus attention should be paid during the promotion of urbanisation processes in rapidly developing cities such as Zhengzhou; however, as the urban population increases, under economic development and a policy of unceasing expansion, the area of inconsistency was mitigated after 2010. Our findings illustrated the influence of consistency on built-up areas and human activities in terms of coordinated development within cities and provided a better understanding of the urbanisation process in Chinese cities.