Details

Autor(en) / Beteiligte

• Wang, Jie
• Dai, Zhijun
• Mei, Xuefei
• Fagherazzi, Sergio

Titel

Tropical Cyclones Significantly Alleviate Mega‐Deltaic Erosion Induced by High Riverine Flow

Ist Teil von

• Geophysical research letters, 2020-10, Vol.47 (19), p.n/a

Ort / Verlag

Washington: John Wiley & Sons, Inc

Erscheinungsjahr

2020

Link zum Volltext

Quelle

Wiley-Blackwell Journals

Beschreibungen/Notizen

• The drastic decline in sediment discharge experienced by large rivers in recent years might trigger erosion thus increasing the vulnerability of their extensive deltas. However, scarce information is available on the erosion patterns in mega‐deltas and associated physical drivers. Here a series of bathymetries in the South Passage, Changjiang Delta, were analyzed to identify morphodynamic variations during high riverine flow and tropical cyclones (TCs). Results indicate that high river flow during flood season triggers large‐scale net erosion along the inner estuary, generating elongated erosion‐deposition patches. Erosion magnitude gradually weakens moving seaward with few localized bottom variations in the offshore area. TCs transport sediment landward and are accompanied by an overall weak erosion, with a less organized spatial pattern of erosion‐deposition. TCs can therefore significantly alleviate erosion, reducing the sediment loss induced by riverine flows by over 50%. These results highlight the role of TCs on the sediment dynamics of mega‐deltas. Plain Language Summary In recent years, climate change and reduced riverine sediment inputs have significantly affected the morphology of large deltas. However, it is unknown whether typhoons cause erosion or deposition in the submerged part of a delta, due to challenge in capturing infrequent events. Here we study the impact of high river flow and typhoons on the South Passage, Changjiang Delta. Results show that high riverine flows can cause large‐scale erosion. Typhoons reduce fluvial erosion by transporting offshore sediments in the delta. The relative accretion caused by a typhoon is more than half the net erosion induced by riverine floods. This research sheds light on the sediment budget of large deltas and inform policy measures that can mitigate the effect of increasing anthropogenic pressure, extreme events, and sea level rise on delta morphology. Key Points High riverine flow during the flood season triggers massive erosion in the Changjiang Delta Tropical cyclones reduce the overall fluvial erosion during the flood season Deposition triggered by typhoons can offset 50% of the estuarine erosion caused by high riverine flow