Coastal Environments and Global Change

12Estuaries and Tidal Inlets

Duncan FitzGerald¹, Ioannis Georgiou² and Michael Miner³

¹ Department of Earth and Environment, Boston University, Boston, MA, USA

² Department of Earth and Environmental Sciences, University of New Orleans, New Orleans, LA, USA

³ Marine Minerals Program, Bureau of Ocean Energy Management, Gulf of Mexico Region, New Orleans, LA, USA

12.1 Introduction

This chapter is devoted to estuaries and tidal inlets – coastal systems that are closely related, but also have important differences. Both are waterways that provide navigation to ports, exchange of nutrients with the coastal ocean, and access to important feeding and breeding grounds for fin and shellfish. Estuaries most commonly occur at mouths of rivers, whereas tidal inlets are associated with barrier shorelines. The dimensions of tidal inlets and the distribution of their associated sand bodies are controlled by the volume and strength of tidal flow, sediment supply, and wave energy. Estuaries exist in a wide range of geological settings, including rias, glaciated valleys, structural basins, and bar-built systems. In the northern hemisphere, rising sea level following deglaciation flooded the incised valleys of river systems. These drowned valleys formed estuaries, except in cases where rivers with high sediment loads filled their channels (valleys) even though rising sea level continued to flood their valleys, resulting in the development of deltas (see Chapter 13). The distribution of estuarine-associated ...