Abstract
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.
Highlights
The surface landscape is often fundamentally altered during economic and social development, and quantity, morphology, and structure of river systems are usually inadvertently influenced along with land use change [1,2,3]
We have presented and applied a method of grid river density on a river network plain in Eastern China to reveal the impact of land use change on a river system in Suzhou City, a city that has gone through a period of rapid population growth and human development
In 1983, the proportion of built-up land was only 10.12% while the proportion of cultivated land was up to 62.05% (Table 2), which indicates that agriculture played a decisive role in the economic and social developments before 1983
Summary
The surface landscape is often fundamentally altered during economic and social development, and quantity, morphology, and structure of river systems are usually inadvertently influenced along with land use change [1,2,3]. Wolman [5] further revealed how river channels respond to three stages of urban development: an equilibrium pre-development stage; a period of construction during which bare land is exposed to erosion, leading to sedimentation within river channels; a stage of urban landscape that is dominated by an impervious surface, leading to increased runoff and decreased sediment production, followed by continued river channel erosion from increased runoff coupled with a decline in sediment that yield enlarged river channels. The hydro-geomorphic response to land use change is further amplified when river systems are deliberately modified—to meet the needs. Water 2018, 10, 609 of human development (e.g., agricultural modification, industrialization, urbanization)—through reshaping, widening, occupation and burial, etc. [7], and has been identified as one of the most widespread and dramatic influences on river systems since the middle of the twentieth century [1].
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