Hydrological controls on the evolution of the Yellow River Delta: An evaluation of the relationship since the Xiaolangdi Reservoir became fully operational

Abstract

The Xiaolangdi Reservoir, which was constructed in the trunk of the Yellow River, has controlled the flow process into the mouth of the Yellow River to a significant degree since it began fully operating in late 2002. To evaluate the relationship between the new hydrological process and the evolution of the Yellow River estuary, this study presents a detailed investigation of the morphodynamic adjustment in the river mouth using remote sensing satellite images. It was shown that the mouth channel rapidly extended in length from 2002 to 2004, although it was shrinking during 1999-2001, and then it expanded very slowly with considerable shifts at the place where the river flow mixes with seawater. In late 2007, an avulsion occurred on the northern bank of the mouth channel, far upstream from where the river water mixes with seawater. During 2008-2012, the new mouth channel extended its length intothe sea at a slow pace, whereas since late 2013, it has divided into two branches that alternately discharge the main flow into the sea. Although both the water and the sediment input in the new hydrological process are much smaller in quantity than before, the geomorphic adjustments still manifest an excessive input of both. Moreover, after the avulsion, the seasonal pattern of land accretion in the river mouth has been characterized, with erosion occurring mostly in the wet seasons and accretion mostly occurring in the dry seasons.

A Tale of Two Deltas: Dam-Induced Hydro-Morphological Evolution of the Volta River Delta (Ghana) and Yellow River Delta (China)

“…The two deltas were selected for the following reasons. Firstly, the Volta River and Yellow River are both heavily regulated by dams, and the sediment supply, frequency and peak discharge of floods have reduced remarkably under dam regulation [19,22,23]. Secondly, both deltas have shifted or are shifting from river-dominated to wave-dominated deltas due to reduced sediment load [9,[24][25][26][27].…”

“…Secondly, both deltas have shifted or are shifting from river-dominated to wave-dominated deltas due to reduced sediment load [9,[24][25][26][27]. Thirdly, both deltas play a critical role in the local economy and ecosystem [19,22]. Our comparative study aimed to examine lessons and experiences in selected deltas to inform other similar deltas worldwide.…”

Decadal link between longitudinal morphological changes in branching channels of Yangtze estuary and movement of the offshore depo‐center

“…The latter processes are usually related to local erosion or deposition in estuarine systems, and are caused by variations in sediment load, runoff discharge and local hydrodynamics due to human interference. For example, reduction in fluvial sediment load due to the trapping effect of river dams has led to widespread recession of river deltas around the world (Rao et al, 2010; Maloney et al, 2018; Zhu et al, 2019), whereas runoff regulation of river dams has triggered depositional features (Frihy and Lawrence, 2004; Zamora et al, 2013) and altered spatial erosion–deposition distributions in estuaries (Zhu et al, 2017, 2018). Moreover, estuarine engineering projects interfere with local hydrodynamics and adjust nearby erosion–deposition patterns (Nitsche et al, 2007; Liu et al, 2009; Luan et al, 2016; El Jakani et al, 2019).…”

“…Consequently, offshore depo‐centers are useful indicators of offshore and continental evolution processes. Although researchers have investigated decadal to seasonal morphological changes caused by human disturbances within inland and near‐mouth areas (Frihy and Lawrence, 2004; Nitsche et al, 2007; Rao et al, 2010; Zamora et al, 2013; Luan et al, 2016; Zhu et al, 2017; Maloney et al, 2018; Zhou et al, 2018; El Jakani et al, 2019; Zhu et al, 2019), longitudinal erosion–deposition patterns within inland estuarine channels (i.e. differences in morphological behavior between upper and lower sub‐reaches of the channels) have not been systematically studied to date.…”

Erosion-deposition patterns and depo-center movements in branching channels at the near-estuary reach of the Yangtze River

“…channel improvement works, and sand excavation) (Kuang et al, 2014;Zheng et al, 2018;Dai and Ding, 2019), and Coriolisinduced circulation in estuarine areas (Wang et al, 2013;Li et al, 2011Li et al, , 2014. Dams modulate runoff discharge in rivers worldwide and can drive the morphological evolution of braided reaches, as demonstrated by many inland rivers (Petts and Gurnell, 2005;Graf, 2006;Han et al, 2018;Alcayaga et al, 2019;Mendoza et al, 2019; and estuarine areas (Warne et al, 2002;Sloff et al, 2013;Zhu et al, 2017;Liu et al, 2018;Zhou et al, 2018), noting that tidal discharges are relatively stable at the yearly time scale (Horrevoets et al, 2004;Jiang et al, 2012a;Zhu et al, 2017). For fluvial braided reaches, shrinking or developing trends of branching channels are often aggravated or interchanged after dam impoundment, caused by changes in unidirectional flow dynamics driven by the altered runoff discharge (Han et al, 2018;Zhu et al, 2019).…”