Oceanography The Official Magazine of
The Oceanography Society
Volume 30 Issue 03

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Volume 30, No. 3
Pages 10 - 21

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FROM THE GUEST EDITORS • Introduction to the Special Issue on Sedimentary Processes Building a Tropical Delta Yesterday, Today, and Tomorrow: The Mekong System

By Charles A. Nittrouer , Julia C. Mullarney, Mead A. Allison, and Andrea S. Ogston 
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Article Abstract

River deltas are important for human habitation, commerce, food, and natural resources. Most terrestrial freshwater, dissolved substances, and suspended sediment supplied to the ocean pass through delta distributary channels. Transitions are complex as this river discharge moves through the serial environments of delta systems: tidal river, estuary, shoreline, continental shelf.

The bulk of Mekong sediment accumulates as a muddy clinoform deposit on the shallow continental shelf (<20–25 m water depth), which forms the foundation over which the subaerial delta surface has grown for the past ~8,000 years. The Song Hau distributary channel, the target of this investigation, receives ~40% of the Mekong discharge and transfers the majority of it to the adjacent shelf during high flow of the river (July–November). Some of the sediment is returned to the channel and to the mangrove shoreline during low flow of the river (December–April). The sediment reentering the channel is mostly mud, deposited by estuarine processes, that temporarily buries the channel bed and interrupts sand transfer to the coastal ocean.

Trapping of sediment supplied to the shoreline of the island, Cu Lao Dung, at the Song Hau mouth, is enhanced by the roughness from dense mangrove roots extending above the bed. Shoreline progradation is asymmetric with the most rapid sediment accumulation (~5 cm yr–1) in the southwestern portion of the island, and the distribution of mangroves is linked to this sedimentation pattern. About one-third of Mekong sediment discharge accumulates in the shelf clinoform near the mouths of the distributary channels, with the greatest accumulation rates (>10 cm yr–1) in the relatively steep foreset region. Intense landward and southwestward currents transport the other two-thirds of Mekong discharge during energetic shelf conditions (December–April). These sediments create a relatively shallow clinoform structure, cause the delta to grow asymmetrically toward the southwest, and form the Ca Mau Peninsula.

In the future, these same natural processes will operate under different conditions. Construction of many dams within the drainage basin (>200 constructed or approved) and the impacts of climate change (i.e., alterations in monsoonal conditions) will significantly decrease Mekong River discharge. In addition, the delta land surface will be flooded due to acceleration of eustatic sea level rise and local land subsidence. Together, loss of river discharge and rise of local sea level will cause many secondary impacts, including erosion of distributary channels, ocean shorelines, and the shelf seabed; saltwater intrusion farther into the channels, along with transfer of associated estuarine processes; and decreased supply of freshwater and solutes, including nutrients, to the coastal ocean. The collaborative research among international and Vietnamese scientists described in this special issue of Oceanography provides an integrated understanding of the Mekong Delta system, and could help formulate strategies to enhance the resiliency of the system and its ability to cope with future impacts.

Citation

Nittrouer, C.A., J.C. Mullarney, M.A. Allison, and A.S. Ogston. 2017. Introduction to the special issue on sedimentary processes building a tropical delta yesterday, today, and tomorrow: The Mekong System. Oceanography 30(3):10–21, https://doi.org/10.5670/oceanog.2017.310.

References

Albers, T., and K. Schmitt. 2015. Dyke design, floodplain restoration and mangrove co-management as parts of an area coastal protection strategy for the mud coasts of the Mekong Delta, Vietnam. Wetlands Ecology Management 23:991–1,004, https://doi.org/10.1007/s11273-015-9441-3.

Allison, M.A., C.A. Nittrouer, A.S. Ogston, J.C. Mullarney, and T.T. Nguyen. 2017. Sedimentation and survival of the Mekong Delta: A case study of decreased sediment supply and accelerating rates of relative sea level rise. Oceanography 30(3):98–109, https://doi.org/​10.5670/oceanog.2017.318.

Allison, M.A., H.D. Weathers III, and E.A. Meselhe. In press. Bottom morphology in the Song Hau distributary channel, Mekong River Delta, Vietnam. Continental Shelf Research, https://doi.org/10.1016/​j.csr.2017.05.010.

Anthony, E.J., G. Brunier, M. Besset, M. Goichot, P. Dussouillez, and V.L. Nguyen. 2015. Linking rapid erosion of the Mekong River delta to human activities. Scientific Reports 5, https://doi.org/10.1038/srep14745.

Besset, M., E.J. Anthony, G. Brunier, and P. Dussouillez. 2016. Shoreline change of the Mekong River delta along the southern part of the South China Sea coast using satellite image analysis (1973–2014). Geomorphologie-Relief Processus Environnement 22:137–146.

Bravard, J.P., M. Goichot, and H. Tronchere. 2014. An assessment of sediment-transport processes in the Lower Mekong River based on deposit grain sizes, the CM technique and flow-energy data. Geomorphology 207:174–189, https://doi.org/​10.1016/j.geomorph.2013.11.004.

Brunier, G., E.J. Anthony, M. Goichot, M. Provansal, and P. Dussouillez. 2014. Recent morphological changes in the Mekong and Bassac river channels, Mekong Delta: The marked impact of river-bed mining and implications for delta destabilization. Geomorphology 224:177–191, https://doi.org/​10.1016/j.geomorph.2014.07.009.

Bryan, K.R., W. Nardin, J.C. Mullarney, and S. Fagherazzi. In press. The role of cross-shore tidal dynamics in controlling intertidal sediment exchange in mangroves in Cu Lao Dung, Vietnam. Continental Shelf Research, https://doi.org/10.1016/​j.csr.2017.06.014.

Bullock, E.L., S. Fagherazzi, W. Nardin, P. Vo-Luong, P. Nguyen, and C.E. Woodcock. In press. Temporal patterns in species zonation in a mangrove forest in the Mekong Delta, Vietnam, using a time series of Landsat imagery. Continental Shelf Research, https://doi.org/10.1016/j.csr.2017.07.007.

Darby, S.E., C.R. Hackney, J. Leyland, M. Kummu, H. Lauri, D.R. Parsons, J.L. Best, A.P. Nicholas, and R. Aalto. 2016. Fluvial sediment supply to a megadelta reduced by shifting tropical-​cyclone activity. Nature 539:276–279, https://doi.org/​10.1038/nature19809.

DeMaster, D.J., J.P. Liu, E. Eidam, C.A. Nittrouer, and T.T. Nguyen. In press. Determining rates of sediment accumulation on the Mekong shelf: Timescales, steady-state assumptions, and radiochemical tracers. Continental Shelf Research, https://doi.org/10.1016/j.csr.2017.06.011.

Eidam, E.F., C.A. Nittrouer, A.S. Ogston, D.J. DeMaster, J.P. Liu, T.T. Nguyen, T.N. Nguyen. In press. Dynamic controls on shallow clinoform geometry: Mekong Delta, Vietnam. Continental Shelf Research, https://doi.org/10.1016/j.csr.2017.06.001.

Erban, L.E., St.M. Gorelick, and H.A. Zebker. 2014. Groundwater extraction, land subsidence, and sea-level rise in the Mekong Delta, Vietnam. Environmental Research Letters 9(8):084010, https://doi.org/10.1088/1748-9326/9/8/084010.

Fagherazzi, S., K.R. Bryan, and W. Nardin. 2017. Buried alive or washed away: The challenging life of mangroves in the Mekong Delta. Oceanography 30(3):48–59, https://doi.org/​10.5670/oceanog.2017.313.

Fricke, A.T., C.A. Nittrouer, A.S. Ogston, and H.P. Vo-Luong. In press. Asymmetric progradation of a coastal mangrove forest controlled by combined fluvial and marine influence, Cù Lao Dung, Vietnam. Continental Shelf Research, https://doi.org/​10.1016/j.csr.2017.07.012.

Hanebuth, T.J., U. Proske, Y. Saito, V. Nguyen, and K.O.T. Thi. 2012. Early growth stage of a large delta: Transformation from estuarine-platform to deltaic-progradational conditions (the northeastern Mekong River Delta, Vietnam). Sedimentary Geology 261:108–119, https://doi.org/10.1016/​j.sedgeo.2012.03.014.

Henderson, S.M., B.K. Norris, J.C. Mullarney, and K.R. Bryan. In press. Wave-frequency flows within a near-bed vegetation canopy. Continental Shelf Research, https://doi.org/10.1016/j.csr.2017.06.003.

Kondolf, G.M., Z.K. Rubin, and J.T. Minear. 2014. Dams on the Mekong: Cumulative sediment starvation. Water Resources Research 50(6):5,158–5,169, https://doi.org/10.1002/2013WR014651.

Kummu, M., and O. Varis. 2007. Sediment-related impacts due to upstream reservoir trapping, the Lower Mekong River. Geomorphology 85:275–293, https://doi.org/10.1016/j.geomorph.2006.03.024.

Li, X., J.P. Liu, Y. Saito, and V.L. Nguyen. In press. Recent evolution of the Mekong Delta and the impact of dams. Earth Science Review.

Liu, C., Y. He, D.E. Walling, and J.J. Wang. 2013. Changes in the sediment load of the Lancang- Mekong River over the period 1965–2003. Science China Technological Sciences 56(4):843–852, https://doi.org/10.1007/s11431-013-5162-0.

Liu, J.P., D.J. DeMaster, T.T. Nguyen, Y. Saito, V.L. Nguyen, T.K.O. Ta, and X. Li. 2017. Stratigraphic formation of the Mekong River Delta and its recent shoreline changes. Oceanography 30(3):72–83, https://doi.org/10.5670/oceanog.2017.316.

Liu, J.P., D.J. DeMaster, C.A. Nittrouer, E.F. Eidam, and T.T. Nguyen. In press. A seismic study of the Mekong subaqueous delta: Proximal versus distal accumulation. Continental Shelf Research, https://doi.org/10.1016/j.csr.2017.07.009.

Loisel, H., A. Mangin, V. Vantrepotte, D. Dessailly, D. Ngoc Dinh, P. Garnesson, S. Ouillon, J.P. Lefebvre, X. Meriaux, and T. Minh Phan. 2014. Variability of suspended particulate matter concentration in coastal waters under the Mekong’s influence from ocean color (MERIS) remote sensing over the last decade. Remote Sensing of Environment 150:218–230.

Lu, X.X., M. Kummer, and C. Oeumg. 2014. Reappraisal of sediment dynamics in the Lower Mekong River, Cambodia. Earth Surface Processes and Landforms 39:1,855–1,865, https://doi.org/​10.1002/esp.3573.

Lu, X.X., and R.Y. Siew. 2006. Water discharge and sediment flux changes in the Lower Mekong River. Hydrology Earth Systems Science 10:181–195, https://doi.org/10.5194/hess-10-181-2006.

Manh, N.V., N.V. Dung, N.N. Hung, M. Kummu, B. Merz, and H. Apel. 2015. Future sediment dynamics in the Mekong Delta floodplains: Impacts of hydropower development, climate change and sea level rise. Global and Planetary Change 127:22–33, https://doi.org/10.1016/j.gloplacha.2015.01.001.

McLachlan, R.L., A.S. Ogston, and M.A. Allison. In press. Implications of tidally-varying bed stress and intermittent estuarine stratification on fine-​sediment dynamics through the Mekong’s tidal river to estuarine reach. Continental Shelf Research, https://doi.org/10.1016/j.csr.2017.07.014.

Meselhe, E., D. Roelvink, C. Wackerman, F. Xing, and V.Q. Thanh. 2017. Modeling the process response of coastal and deltaic systems to human and global changes: Focus on the Mekong system. Oceanography 30(3):84–97, https://doi.org/​10.5670/oceanog.2017.317.

Milliman, J.D., and R.H. Meade. 1983. World-wide delivery of river sediment to the oceans. The Journal of Geology 91:1–21, https://doi.org/​10.1086/628741.

Minderhoud, P.S.J., G. Erkens, V.H. Pham, V.T. Bui, L. Erban, H. Kooi, and E. Stouthamer. 2017. Impacts of 25 years of groundwater extraction on subsidence in the Mekong Delta, Vietnam. Environmental Research Letters 12:064006, https://doi.org/​10.1088/1748-9326/aa7146.

Mullarney, J.C., S.M. Henderson, B.K. Norris, K.R. Bryan, A.T. Fricke, D.R. Sandwell, and D.P. Culling. 2017. A question of scale: How turbulence around aerial roots shapes the seabed morphology in mangrove forests of the Mekong Delta. Oceanography 30(3):34–47, https://doi.org/​10.5670/oceanog.​2017.312.

Mullarney, J.C., S.M. Henderson, J.A.H. Reyns, B.K. Norris, and K.R. Bryan. In press. Spatially varying drag within a wave-exposed mangrove forest and on the adjacent tidal flat. Continental Shelf Research, https://doi.org/10.1016/j.csr.2017.06.019.

Nardin, W., C.E. Woodcock, and S. Fagherazzi. 2016. Bottom sediments affect Sonneratia mangrove forests in the prograding Mekong Delta, Vietnam. Estuarine, Coastal and Shelf Science 177:60–70, https://doi.org/10.1016/j.ecss.2016.04.019.

Nguyen, A.D., H.H.G. Savenije, D.N. Pham, and D.T. Tang. 2008. Using salt intrusion measurements to determine the freshwater discharge distribution over the branches of a multi-channel estuary: The Mekong Delta case. Estuarine, Coastal, and Shelf Science 77:433–445, https://doi.org/10.1016/​j.ecss.2007.10.010.

Nguyen, T.T.X., and C.D. Woodroffe. 2016. Assessing relative vulnerability to sea-level rise in the western part of the Mekong River Delta in Vietnam. Sustainability Science 11:645–659, https://doi.org/​10.1007/s11625-015-0336-2.

Nguyen, V.L., T.K.O. Ta, and M. Tateishi. 2000. Late Holocene depositional environments and coastal evolution of the Mekong River Delta, southern Vietnam. Journal of Asian Earth Sciences 18:427–439, https://doi.org/10.1016/S1367-9120(99)00076-0.

Nguyen, V.L., T.K.O. Ta, M. Tateishi, I. Kobayashi, and Y. Saito. 2005. Holocene evolution of the Mekong River delta, Vietnam. Journal of the Geological Society of Japan 111(11):XXI, https://doi.org/10.5575/geosoc.111.11.XXI.

Nittrouer, C.A., G.J. Brunskill, and A.G. Figueiredo. 1995. The importance of tropical coastal environments. Geo-Marine Letters 15:121–126, https://doi.org/​10.1007/BF01204452.

Nittrouer, C.A., D.J. DeMaster, E.F. Eidam, T.T. Nguyen, J.P. Liu, A.S. Ogston, and P.V. Phung. 2017. The Mekong continental shelf: The primary sink for deltaic sediment particles and their passengers. Oceanography 30(3):60–70, https://doi.org/​10.5670/oceanog.2017.314.

Noh, S., M. Choi, E. Kim, N.P. Dan, B.X. Thanh, N.T.V. Ha, S. Sthiannopkao, and S. Han. 2013. Influence of salinity intrusion on the speciation and partitioning of mercury in the Mekong River delta. Geochimica et Cosmochimica Acta 106:379–390, https://doi.org/10.1016/j.gca.2012.12.018.

Norris, B.K., J.C. Mullarney, K.R. Bryan, and S.M. Henderson. In press. The effect of pneumatophore density on turbulence: A field study in a Sonneratia-dominated mangrove forest, Vietnam. Continental Shelf Research, https://doi.org/10.1016/​j.csr.2017.06.002.

Nowacki, D.J., A.S. Ogston, C.A. Nittrouer, A.T. Fricke, and P.D.T. Van. 2015. Sediment dynamics in the lower Mekong River: Transition from tidal river to estuary. Journal of Geophysical Research: Oceans 120:6,363–6,383, https://doi.org/​10.1002/​2015JC010754.

Ogston, A.S., M.A. Allison, R.L. McLachlan, D.J. Nowacki, and J.D. Stephens. 2017. How tidal processes impact the transfer of sediment from source to sink: Mekong River collaborative studies. Oceanography 30(3):22–33, https://doi.org/​10.5670/oceanog.2017.311.

Phan, L.K., J.S.M. de Vries, and M.J.F. Stive. 2015. Coastal mangrove squeeze in the Mekong Delta. Journal of Coastal Research 31(2):233–243, https://doi.org/10.2112/JCOASTRES-D-14-00049.1.

Schimanski, A., and K. Stattegger, K. 2005. Deglacial and Holocene evolution of the Vietnam shelf: Stratigraphy, sediments and sea-level change. Marine Geology 214:365–387, https://doi.org/​10.1016/j.margeo.2004.11.001.

Schmitt, K., T. Albers, T.T Pham, and S.C. Dinh. 2013. Site-specific and integrated adaptation to climate change in the coastal mangrove zone of Soc Trang Province, Viet Nam. Journal of Coastal Conservation 17(3):545–558, https://doi.org/​10.1007/s11852-013-0253-4.

Schmitt, R.J.P., Z. Rubin, and G.M. Kondolf. In press. Losing ground: Scenarios of land loss as consequence of shifting sediment budgets in the Mekong Delta. Geomorphology, https://doi.org/​10.1016/j.geomorph.2017.04.029.

Smajgl, A., T.Q. Toan, D.K. Nhan, J. Ward, N.H. Trung, L.Q. Tri, V.P.D. Tri, and P.T. Vu. 2015. Responding to rising sea levels in the Mekong Delta. Nature Climate Change 5(2):167–174, https://doi.org/​10.1038/nclimate2469.

Stanley, D.J., and A.G. Warne. 1994. Worldwide initiation of Holocene marine deltas by deceleration of sea-level rise. Science 265:228–231, https://doi.org/10.1126/science.265.5169.228.

Stephens, J.B., M.A. Allison, D.R. Di Leonardo, H.D. Weathers III, A.S. Ogston, R.L. McLachlan, F. Xing, and E.A. Meselhe. In press. Sand dynamics in the Mekong River channel and export to the coastal ocean. Continental Shelf Research.

Szczuciński, W., R. Jagodziński, T.J.J. Hanebuth, K. Stattegger, A. Wetzel, M. Mitręga, D. Unverricht, and P. Van Phach. 2013. Modern sedimentation and sediment dispersal pattern on the continental shelf off the Mekong River delta, South China Sea. Global and Planetary Change 110:195–213, https://doi.org/10.1016/j.gloplacha.2013.08.019.

Ta, T.K.O., V.L. Nguyen, M. Tateishi, I. Kobayashi, and Y. Saito. 2005. Holocene delta evolution and depositional models of the Mekong River Delta, southern Vietnam. SEPM Special Publication 83:453–466, https://doi.org/10.2110/pec.05.83.0453.

Ta, T.K.O., V. Nguyen, M. Tateishi, I. Kobayashi, S. Tanabe, and Y. Saito. 2002. Holocene delta evolution and sediment discharge of the Mekong River, southern Vietnam. Quaternary Science Reviews 21:1,807–1,819, https://doi.org/10.1016/S0277-3791(02)00007-0.

Takagi, H., T.V. Ty, N.D. Than, and M. Esteban. 2014. Ocean tides and the influence of sea-level rise on floods in urban areas of the Mekong Delta. Journal of Flood Risk Management 8:292–300, https://doi.org/​10.1111/jfr3.12094.

Tamura, T., K. Horaguchi, Y. Saito, V.L. Nguyen, M. Tateishi, T.K.O. Ta, F. Nanayama, and K. Watanabe. 2010. Monsoon-influenced variations in morphology and sediment of a mesotidal beach on the Mekong River delta coast. Geomorphology 116(1):11–23, https://doi.org/​10.1016/j.geomorph.2009.10.003.

Tamura, T., Y. Saito, M.D. Bateman, V.L. Nguyen, T.K.O. Ta, and D. Matsumoto. 2012a. Luminescence dating of beach ridges for characterizing multi-decadal to centennial deltaic shoreline changes during Late Holocene, Mekong River delta. Marine Geology 326–328:140–153, https://doi.org/10.1016/j.margeo.2012.08.004.

Tamura, T., Y. Saito, V.L. Nguyen, T.K.O. Ta, M.D. Bateman, D. Matsumoto, and S. Yamashita. 2012b. Origin and evolution of interdistributary delta plains: Insights from Mekong River delta. Geology 40:303–306, https://doi.org/10.1130/G32717.1.

Tamura, T., Y. Saito, S. Sieng, B. Ben, M. Kong, I. Sim, S. Choup, and F. Akiba. 2009. Initiation of the Mekong River delta at 8 ka: Evidence from the sedimentary succession in the Cambodian lowland. Quaternary Science Reviews 28:327–344, https://doi.org/10.1016/j.quascirev.2008.10.010.

Thanh, V.Q., J. Reyns, C. Wackerman, E.F. Eidam, and D. Roelvink. In press. Modelling suspended sediment dynamics on the subaqueous delta of the Mekong River. Continental Shelf Research, https://doi.org/10.1016/j.csr.2017.07.013.

Thu, P.M., and J. Populus. 2007. Status and changes of mangrove forest in Mekong Delta: Case study in Tra Vinh, Vietnam. Estuarine, Coastal and Shelf Science 71(1–2):98–109, https://doi.org/10.1016/j.ecss.2006.08.007.

Tjallingii, R., K. Stattegger, A. Wetzel, and V.P. Phung. 2010. Infilling and flooding of the Mekong River incised valley during deglacial sea-level rise. Quaternary Science Reviews 29:1,432–1,444, https://doi.org/10.1016/j.quascirev.2010.02.022.

Unverricht, D., T.C. Nguyen, C. Heinrich, W. Szczuciński, N. Lahajnar, and K. Stattegger. 2014. Suspended sediment dynamics during the inter-monsoon season in the subaqueous Mekong Delta and adjacent shelf, southern Vietnam. Journal of Asian Earth Sciences 79:509–519, https://doi.org/10.1016/j.jseaes.2012.10.008.

Unverricht, D., W. Szczuciński, K. Stattegger, R. Jagodziński, X.T. Le, and L.L.W. Kwong. 2013. Modern sedimentation and morphology of the subaqueous Mekong Delta, southern Vietnam. Global Planetary Change 110:223–235, https://doi.org/​10.1016/j.gloplacha.2012.12.009.

Vinh, V.D., S. Ouillon, N.V. Thao, N.N. Tien, 2016. Numerical simulations of suspended sediment dynamics due to seasonal forcing in the Mekong coastal area. Water 8(6):255, https://doi.org/​10.3390/w8060255.

Wackerman, C., A. Hayden, and J. Jonik. In press. Deriving spatial and temporal context for point measurements of suspended sediment concentration using remote sensing imagery in the Mekong Delta. Continental Shelf Research.

Wang, J.J., X.X. Lu, and M. Kummu. 2011. Sediment load estimates and variations in the lower Mekong River. River Research and Applications 27:33–46, https://doi.org/10.1002/rra.1337.

Wassman, R., N.X. Hein, C.T. Hoanh, and T.P. Tuong. 2004. Sea level rise affecting the Vietnamese Mekong Delta: Water elevation in the flood season and implications for rice production. Climate Change 66:89–107, https://doi.org/10.1023/​B:CLIM.0000043144.69736.b7.

Wolanski, E., N.N. Huan, L.T. Dao, N.H. Nhan, and N.N. Thuy. 1996. Fine-sediment dynamics in the Mekong River estuary, Vietnam. Estuarine, Coastal, and Shelf Science 43:565–582, https://doi.org/​10.1006/ecss.1996.0088.

Wolanski, E., N.H. Nhan, and S. Spagnol. 1998. Sediment dynamics during low flow conditions in the Mekong River estuary, Vietnam. Journal of Coastal Research 14(2):472–482.

Xing, F., E.A. Meselhe, M.A. Allison, and H.D. Weathers III. In press. Analysis and numerical modeling of the flow and sand dynamics in the lower Song Hau channel, Mekong Delta. Continental Shelf Research.

Xue, Z., R. He, J.P. Liu, and J.C. Warner. 2012. Modeling transport and deposition of the Mekong River sediment. Continental Shelf Research 37:66–78, https://doi.org/10.1016/​j.csr.2012.02.010.

Xue, Z., J.P. Liu, D.J. DeMaster, L. Van Nguyen, and T.K.O. Ta. 2010. Late Holocene evolution of the Mekong subaqueous delta, southern Vietnam. Marine Geology 269:46–60, https://doi.org/​10.1016/j.margeo.2009.12.005.

Xue, Z., J.P. Liu, and Q.A. Ge. 2011. Changes in hydrology and sediment delivery of the Mekong River in the last 50 years: Connection to damming, monsoon, and ENSO. Earth Surface Processes and Landforms 36:296–308, https://doi.org/10.1002/esp.2036.

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