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River systems are crucial for the Earth system. However, they are profoundly impacted by human activities, especially land use change. To reveal the impact of land use change on river systems, river system data and land use data in Suzhou City from the 1960s to 2010s were analyzed through grid river density on a 3 km × 3 km scale. The spatial-temporal variation was very different for different river orders. The lower the river order, the larger was the variation in the accumulated length (including both an increase and a decrease). The river systems were modified to meet the needs of human development in different social development stages. During the period of agricultural modification, undeveloped land was reclaimed to increase the amount of arable land available, but when the proportion of cultivated land exceeded a threshold level, higher order rivers were invaded, cut off and even buried, which forced a part of the higher order rivers to transform into narrower rivers. During the period of urbanization, higher order rivers were usually dredged, reconstructed and protected to improve the abilities of storage and discharge, and lower order rivers were buried after 40% of the land proportion had been built up. These results provide a reliable foundation on which to formulate policies and manage river systems.

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Owing to the crucial environmental and hydrological functions of river systems and intensive human disturbance, further investigations of their change patterns and flood control functions are urgently needed. The Rapidly Urbanized Taihu Basin (RUTB) was selected as the study region to investigate changes in the river networks, the relationship between changes in river systems and urbanization, and the changes in the static drainage storage capacity (SC) and regulation capacity (RC) from the 1980s to the 2010s. The results indicated that the total drainage density in RUTB decreased by 10.17%. For the first-, second-, and third-order rivers, the changes are +7.61%, −14.35%, and −17.84%, respectively. Spatially, the change pattern of the third-order river drainage density displayed significant spatial clustering. The ratio of main to tributary river length (Rmt) was increased from 0.31 in the 1980s to 0.39 in the 2010s. Spatially, the drastic increases were found in the south-east of Wu-Cheng-Xi-Yu, the east of Yang-Cheng-Dian-Mao, and the central southern part of Hang-Jia-Hu. Results moreover show that urbanization has the greatest influence on the third-order drainage density, especially around the secondary and rapidly developing cities. The demand for flood control has led to a slight increase in the density of main rivers. The values of SC and RC decreased by 0.69% and 40.61% in RUTB, respectively. These changes were mainly concentrated around the major cities and urban corridors. The decrease in SC was caused by the decay of the river system, and the reduction in RC was caused by a combination of river system degradation and increase in ordinary water levels.