levee system
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2022 ◽  
Vol 9 ◽  
Author(s):  
Elena Scacchia ◽  
Roberto Tinterri ◽  
Fabiano Gamberi

Overbank deposits provide a potentially valuable record of flows that have passed through a submarine channel. The architecture of overbank deposits has generally assumed to relate to autogenic processes related to channel construction. In previous models, which are largely based on passive margins, the distribution and geometry of these deposits is relatively simple, and hence generally predictable. Here, we show how the interaction of different flow types with the complex morphology on a highly-tectonically modified margin can profoundly affect overbank depositional processes, and hence also the resultant deposit geometry and architecture. Our case study is the Acquarone Fan, located in the intraslope Gioia Basin in the south-eastern Tyrrhenian Sea, whose topography is mainly controlled by the presence of the Acquarone structural ridge, which results in the confinement of the left south-west side of the channel-levee system. The research is carried out through analysis of multibeam bathymetric and high-resolution Chirp sub-bottom profiler data. Seven depositional units (Units I-VII) record the recent depositional history of the fan; their thickness has been mapped and their parent flow-types have been interpreted through their seismic response. According to unit thickness maps, two main patterns of deposition are recognized in the overbank area. Their depocenters coincide with different extensive sediment wave fields developed in specific tracts of the right levee and in the frontal splay area. We show that the location of the depocenters varies in time according to the prevalent flow-type and by its interaction with the surrounding seafloor topography and channel planform. We interpret that the lateral confinement of the channel by the structural high generates episodic rebound of the overspilling flow and the inversion of the channel asymmetry. The vertical stratification of the flow strongly influences the overbank deposition where the channel planform has a non-linear shape such as bends and knick-points. In particular, the vertical stratification influences the hydraulic jump size that conditions the amount of overspill and thus the location of overbank depocenters. This study highlights that variations in the sediment distribution and composition on the overbank can be related to the way different flows interact with tectonic setting.


2021 ◽  
Author(s):  
Lucas Walshire ◽  
Joseph Dunbar

This report describes activities performed, results obtained, and conclusions made from an independent technical review of past levee inspections and the proposed remediation plan for the Santa Margarita Levee that surrounds the U.S. Marine Corps Air Station (MCAS) Camp Pendleton. In support of the technical review, ERDC personnel performed a supplemental levee inspection on 19 and 20 November 2019 with MCAS personnel. Previous levee inspections had rated the levee system as Unacceptable due to unwanted vegetation encroaching on the levee right-of-way, which prevents full inspection during flooding. Concerns were raised by the U.S. Fish and Wildlife (USFW) about environmental impacts of the proposed remediation measures and the necessity of such actions. USFW personnel requested an engineering review from an independent party, and ERDC was tasked with performing the independent technical review. The following special report describes the tasks performed and results obtained from the independent technical review.


Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4406
Author(s):  
Tadaharu Ishikawa ◽  
Hiroshi Senoo

The development process and flood control effects of the open-levee system, which was constructed from the mid-18th to the mid-19th centuries, on the Kurobe Alluvial Fan—a large alluvial fan located on the Japan Sea Coast of Japan’s main island—was evaluated using numerical flow simulation. The topography for the numerical simulation was determined from an old pictorial map in the 18th century and various maps after the 19th century, and the return period of the flood hydrograph was determined to be 10 years judging from the level of civil engineering of those days. The numerical results suggested the followings: The levees at the first stage were made to block the dominant divergent streams to gather the river flows together efficiently; by the completed open-levee system, excess river flow over the main channel capacity was discharged through upstream levee openings to old stream courses which were used as temporary floodways, and after the flood peak, a part of the flooded water returned to the main channel through the downstream levee openings. It is considered that the ideas of civil engineers of those days to control the floods exceeding river channel capacity, embodied in their levee arrangement, will give us hints on how to control the extraordinary floods that we should face in the near future when the scale of storms will increase due to the global climate change.


2021 ◽  
Author(s):  
Ricarda Nielsen ◽  
Gabriele Uenzelmann-Neben

<p>Formation of Antarctic Bottom Water (AABW) plays an essential role within Meridional Overturning Circulation and is widely accepted to be the engine of global Thermohaline Circulation (THC), which is sensitive to climate changes. Studying paleo conditions and changes of AABW distribution during warm and cold periods is fundamental to gain knowledge about its interaction and response to climate changes, which helps to understand recent and future changes of THC due to global warming.</p><p>West of Prydz Bay, along MacRobertson Land Shelf area, a recent production of dense shelf water in the Cape Darnley Polynya and outflow as so-called Cape Darnley Bottom Water (CDBW) along the Wild Canyon has been recognized. CDBW contributes around 6-13% to the total circumpolar AABW. In order to understand the paleo conditions of AABW it is necessary to investigate the paleo-evolution of CDBW. To do this, we have studied the formation history of a 200 km long sediment drift (Darnley Drift herein) at the western flank of the Wild Canyon. We utilized more than 13.000 km of multi-channel seismic reflection data and lithological Data of ODP Site 1165.  </p><p>We characterized Darnley Drift to be a mixed turbiditic-contourite drift formed by an interplay of downslope and along-slope processes. During the Oligocene, turbiditic outflow dominated along the later formed Wild Canyon. An onset of CDBW can be inferred during the early Miocene, forming an asymmetric channel-levee system along the Wild Canyon. After the mid-Miocene Climatic Optimum a major climate change occurred, resulting in a strong intensification of bottom currents and major growth of the drift with simultaneous areas of non-deposition and erosion. This was followed by a sharp reduction of sedimentation rates. Since the late Miocene the growth of Darnley Drift is further dominated by contourite bottom currents.</p>


2021 ◽  
Author(s):  
Edouard Durand ◽  
Yann Deniaud ◽  
Sébastien Patouillard

Author(s):  
S. Nazrul Islam

Chapter 10 provides an overview of the Open approach, focusing on its merits, progress, and prospects and showing how it can be more conducive to sustainable development. It shows that the Open approach is not a passive approach but requires sustained activities along many dimensions, including both flood-proofing and flood-regulating measures. The chapter follows the progression of the Open approach. It discusses the reflection of this approach in the European Union’s Directive on Floods and its implementation. It takes note of country level initiatives in many European countries, such as the Netherlands’ “Room for River” project, that conform with the Open approach. The chapter then examines some recent policy changes in the United States regarding the Mississippi levee system that also reflect the Open approach. It also reviews the progress of the Open approach in other parts of the world.


Author(s):  
S. Nazrul Islam

Chapter 9 presents the Cordon approach, describing its methods, reviewing its spread across the world, and analyzing its consequences. It discusses the general relationship between river channels and their floodplains and explains the nurturing functions that regular river inundations perform. The chapter then outlines the instruments of the Cordon approach, such as embankments, floodwalls, channelization, and canalization. It goes on to explain the relationship between the Cordon and the Polder approaches and offers a classification of cordons into different types. The chapter reviews the consequences of the Cordon approach, distinguishing between those for river channels and for floodplains. It provides an overview of the experience of the Cordon approach in different parts of the world, focusing on the United States, Europe, and India. It also presents two case studies of the Cordon approach: the Mississippi levee system in the United States and the Huang He River embankments in China.


AAPG Bulletin ◽  
2020 ◽  
Vol 104 (9) ◽  
pp. 1921-1944
Author(s):  
Manasij Santra ◽  
Peter B. Flemings ◽  
Erik Scott ◽  
P. Kevin Meazell

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