scholarly journals Optimized river diversion scenarios promote sustainability of urbanized deltas

2021 ◽  
Vol 118 (27) ◽  
pp. e2101649118
Author(s):  
Andrew J. Moodie ◽  
Jeffrey A. Nittrouer

Socioeconomic viability of fluvial-deltaic systems is limited by natural processes of these dynamic landforms. An especially impactful occurrence is avulsion, whereby channels unpredictably shift course. We construct a numerical model to simulate artificial diversions, which are engineered to prevent channel avulsion, and direct sediment-laden water to the coastline, thus mitigating land loss. We provide a framework that identifies the optimal balance between river diversion cost and civil disruption by flooding. Diversions near the river outlet are not sustainable, because they neither reduce avulsion frequency nor effectively deliver sediment to the coast; alternatively, diversions located halfway to the delta apex maximize landscape stability while minimizing costs. We determine that delta urbanization generates a positive feedback: infrastructure development justifies sustainability and enhanced landform preservation vis-à-vis diversions.

Author(s):  
S Voronina ◽  
V Babitsky ◽  
A Meadows

A computer model of a non-linear ultrasonic vibrating system with the possibility of autoresonant control is presented in this paper. The system controlled consists of two modules, the first of which is an electromechanical model of an ultrasonic transducer comprising a piezoelectric transducer and a step concentrator. The second module simulates an influence from the machining process. Coefficients of the electromechanical model and its validity were estimated through an identification process based on the experiments with a real ultrasonic transducer. Further, a numerical model of the autoresonant control of this system has been developed. The autoresonant control maintains the resonant regime of oscillation by means of positive feedback, which provides transformation and amplification of the control signal. The model allows the use and comparison of three control strategies depending on the different electrical and mechanical feedback control signals. The results from simulation and from real machining experiments under different control strategies are compared and discussed.


1970 ◽  
Vol 1 (12) ◽  
pp. 107 ◽  
Author(s):  
Sherwood M. Gagliano ◽  
Hyuck J. Kwon ◽  
Johannes L. Van Beek

Coastal Louisiana wetlands are a product of Mississippi River delta building that has occurred over a period of 5,000 years The building process was a gradual one, for riverine and marine processes were very nearly balanced In modern times man's use of the area (flood control, navigation improvement, exploitation of petroleum and other minerals, road building, etc ) has seriously altered the natural balance As a result, overbank flooding has been virtually eliminated and river flow is confined to channels discharging into the outer shelf area Most transported sediment is now deposited in the deep Gulf of Mexico or along the continental shelf Saltwater encroachment in the deltaic estuaries has been detrimental to fauna and flora Even though considerable sediment deposition has resulted from the historic Atchafalaya River diversion and growth of subdeltas, comparative map studies indicate a net land loss rate of 16 5 miles^/year during the last 25 to 30 years Land loss is only one symptom of general environmental deterioration A dynamic management plan is proposed for better utilization of combined freshwater discharge - dissolved solid and transported sediment input from the Mississippi River Controlled flow into estuaries will reduce salinity encroachment and supply badly needed nutrients Large areas of new marshland and estuarme habitat can be built by controlled subdelta diversion Studies of natural subdeltas indicate that these systems are amenable to environmental management, salinities and sediment deposition may be manipulated to enhance desired conditions.


Author(s):  
Y. Jun Xu

Abstract. Many river deltas in the world are vibrant economic regions, serving as transportation hubs, population centres, and commercial hotspots. However, today, many of these deltaic areas face a tremendous challenge with land loss due to a number of factors, such as reduced riverine sediment supply, coastal land erosion, subsidence, and sea level rise. The development of the Mississippi River Deltaic Plain (MRDP) in southeast Louisiana, USA, over the past century is a good example. Since 1932, approximately 4877 km2 of the coastal land of MRDP has become submerged. The lower Mississippi River main channel entering the Gulf of Mexico has become an isolated waterway with both sides losing land. In contrast, large open water areas in the Mississippi River’s distributary basin, the Atchafalaya River basin, have been silted up over the past century, and the river mouth has developed a prograding delta feature at its two outlets to the Gulf of Mexico. The retrospective analysis of this paper makes it clear that the main cause of the land loss in the MRDP is not the decline of riverine sediment, but the disconnection of the sediment sources from the natural flood plains. Future sediment management efforts in the MRDP should focus on restoring the natural connection of riverine sediment supplies with flood plains, rather than solely using channelized river diversion. This could be achieved through controlled overbank flooding (COF) and artificial floods in conjunction with the use of a hydrograph-based sediment availability assessment.


2019 ◽  
Vol 128 (3) ◽  
pp. 228-233 ◽  
Author(s):  
Brianne L. Glazier ◽  
Lynn E. Alden

2006 ◽  
Author(s):  
Holley S. Hodgins ◽  
Kathryn Adair ◽  
Rachel Gordon ◽  
Yaritza Saavedra ◽  
Sara Shiffman ◽  
...  

2011 ◽  
Author(s):  
Kent Harber ◽  
Jamie L. Gorman ◽  
Frank P. Gengaro ◽  
Samantha Butisingh ◽  
Rebecca Ouellette ◽  
...  

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