Effects of in-channel sand excavation on the hydrology of the Pearl River Delta, China

• Published in: Journal of hydrology (Amsterdam) Vol. 343; no. 3; pp. 230 - 239
• Main Authors: Luo, Xian-Lin, Zeng, Eddy Y., Ji, Rong-Yao, Wang, Chao-Pin
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 20.09.2007; Elsevier Science
• Subjects: Anthropogenic activity; Earth sciences; Earth, ocean, space; Exact sciences and technology; Hydrological change; Hydrology. Hydrogeology; Pearl river delta; River morphology; Sand excavation; Delta River; Alaska; Pearl River; Far East; United States; China; USA, Connecticut, West R; China, People's Rep., Zhu R; Canada, Nova Scotia, East R; China, People's Rep; Sand excavation; Hydrological change; Pearl river delta; River morphology; Anthropogenic activity; tributaries; damage; surveys; excavations; slopes; networks; North America; human activity; dredging; navigation; brackish water; morphology; runoff; urbanization; intrusions; sand; depth; channels; Asia; instability; growth
• ISSN: 0022-1694; 1879-2707
• DOI: 10.1016/j.jhydrol.2007.06.019

The hydrology and morphology of the Pearl River Delta (PRD; South China) water system has been predominantly dictated by human activities over the last 20 years. Uncontrolled sand excavation occurred in all 324 tributaries, largely to meet the construction needs arising from the rapid economic growth and urbanization in the region. It was estimated that >8.7 × 10 8 m 3 of sand were excavated from 1986 to 2003 based on field surveys of excavating activities and the river hypsography, resulting in average downcutting depths of 0.59–1.73 m, 0.34–4.43 m, and 1.77–6.48 m in the main channels of the West River, North River, and East River (three major water networks in the PRD), respectively. Consequently, the water levels in upstream of the PRD were decreased by 1.59–3.12 m (Sanshui Station). Uneven sand dredging also caused changes in the divided flow ratio (DFR) between various water courses. For example, the DFR increased by 8.8% at the Sanshui Station on the upper part of the North River network from the early 1980s to 1999. DFRs also increased almost 7.7% at the four major runoff outlets in the eastern side of the PRD. As a result, present brackish-water has intruded upward 10–20 km more than in the 1980s. Apparently, there are two sides to the effects of sand excavation. The positive effects are decreased chances of flooding damages, improved navigating conditions, and more water inputs to rapid economically growing regions. The negative effects include increased grade slope and instability of the riverbank, disruption of navigation in upstream dredging pits during dry seasons, and brackish-water intrusion.