CHAPTER 8: FLUVIAL PROCESSES, PATTERNS AND LANDFORMS
IN DEPTH – Deltas
Delta shapes Deltas have many shapes and sizes. They are named delta after the letter D in the Greek alphabet. 1. Arcuate delta (arc-shaped) This delta has a triangular shape and the apex of the triangle points upstream. It is named after the shape of the Nile delta in Egypt. These deltas are made of coarse sand and gravel which are very porous so there are
many distributaries which rarely meet. Examples: The Po in Italy, which extends at a rate of 12 m per year. The Nile delta in
Egypt. The River Flesk has a small arcuate delta where it enters Lough Leane in County Kerry (See Fig. 42).
2. Bird’s foot delta These deltas form when rivers carry large amounts of fine sediment and there are very few distributaries. Levees are deposited
along any
distributaries that form, and so long finger-like projections extend into the sea forming a delta with a shape similar to that of a bird’s foot. Example: The Mississippi
River, which extends at a rate of 75 m per year.
Delta
3. Estuarine delta This type of delta forms when deposits are dropped in long, narrow lines, like strips, on both sides of the estuary. Example: The Shannon
Estuary.
Fig. 42 The lacustrine delta of the River Flesk, near Killarney, County Kerry