Sediment Distribution, Retention and Morphodynamic Analysis of a River-Dominated Deltaic System

Ehab Meselhe,Kazi Sadid,Ashok Khadka

doi:10.3390/w13101341

Abstract

River deltas have received considerable attention due to coastal land loss issues caused by subsidence, storms, and sea level rise. Improved understanding of deltaic processes and dynamics is vital to coastal restoration efforts. This paper describes the application of process-based morphodynamic models to a prograding river delta. The analysis focuses on the flow and sediment dynamics amongst the interconnected channel network of the delta. The models were validated against observations of velocity and sediment concentrations for the Wax Lake Delta (WLD) of the Atchafalaya River system in Louisiana, USA. The WLD provides an opportunity as a natural laboratory for studying the processes associated with river dominated deltaic growth. It includes a network of bifurcated channels that self-organize and dynamically adjust, as the delta grows seaward to the Gulf of Mexico. The model results for a flood event show that 47% of the flow exits the system as channelized flow and the remaining 53% exits as overbank flow. The fine sediment (silt and clay) distribution was proportional with water fluxes throughout the channel network, whereas sand distribution was influenced by geometric attributes (size, invert elevation, and alignment) of the distributary channels. The long-term deltaic growth predicted by the model compares well with the observations for the period 1998–2012. This paper provides insights on how the distribution of flow and sediment amongst the interconnected delta channels influences the morphodynamics of the delta to reach a dynamic equilibrium within this relatively young deltaic system.

Highlights

River deltas have received considerable attention due to coastal land loss issues caused by subsidence, sea level rise, and extreme weather events [5]
In the case of the Lower Mississippi River Delta (LMRD), limited sediment supply to wetlands due to upstream dam construction and flood protection levees has contributed to wetland losses
This study aims to gain understanding of flow and sediment dynamics in the channel network of a river delta system

Summary

Introduction

Deltas are complex depositional features developed from river mouth sediment deposition and dispersal [1,2]. They are a preferred human habitat, with a population of over half a billion residing in major coastal cities [3,4]. River deltas have received considerable attention due to coastal land loss issues caused by subsidence, sea level rise, and extreme weather events [5]. Human activities such as river modification, hydrocarbons, and ground water extraction have further exacerbated land loss in modern deltas [1]. Sediment diverted to the shallow receiving basin would allow the river to build new land and sustain existing wetland areas

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Discussion

Conclusion