What Are The Characteristics Of Coastal Plains?

The sea is involved in the development of many geographical features. The majority of coastal areas have plains associated with them. There are many benefits and advantages to coastal plains, and it is worth investigating their characteristics.

Coastal plains have two borders: the ocean on one side and the mountains on the other. Rivers, streams, and deltas characterize coastal plains, with evidence of erosion or deposition processes. Soil may be fertile or sandy, and rocky. These plains are heavily populated and vulnerable to flooding.

Coastal plains have become essential areas in the development of cities and ports. 

What Are The Features Of Coastal Plains?

  • Coastal plains are flat or slightly sloping low-lying land adjacent to the ocean. Together with the beaches, they form an interface between the sea and the land.
  • Coastal plains are bordered by the ocean on one side and other geographical features such as mountains or an escarpment on the other. The landward side of the coastal plain is known as the fall line.
  • Coastal plains have many waterways, rivers, and deltas.
  • The soil may be rich and fertile or sandy.
  • Coastal plains are vulnerable to flooding from severe weather events.
  • Fifty to sixty percent of the total world population lives on coastal plains. 

Why Are Coastal Plains Flat Or Sloping?

Coastal plains develop in one of two ways.

  • A flat section of the continental shelf that lies under the sea becomes exposed when the ocean level falls. The exposure of this section of the continental shelf results in a flat coastal plain.

The fall of the ocean level generally occurred millions of years ago. Evidence for this theory can be seen when aquatic animal fossils are found far inland. An example is fossils of marine organisms found in landlocked Kansas.

  •  A sloping coastal plain results from the deposition of material by river deltas that flood the area, leaving silt and debris when the water recedes. Waves wash up ocean debris onto the beach or carry it inland during high tides, adding to the development of the plain.

Erosion of cliffs and headlands results in the fall of rocks and soil, which add to the deposition. These materials create a coastal plain that slopes gently down to the sea. This kind of coastal plain features an irregular, indented coastline.

What Borders Coastal Plains?

Coastal plains are bordered on one side by the ocean, which changes the shape of the coast by means of erosion and deposition. The plain is continually being extended through biological, mechanical, and chemical weathering and erosion.

Deposition of materials carried by rivers or the ocean results in the development of new features. Coastal accretion from ocean deposition extends the plain out towards the sea, forcing the water level to fall. 

The landside of coastal plains is bordered by mountains or escarpments, which lead to plateaus. In plains characterized by erosion, there will be rugged cliffs and high mountains. The bedrock in the mountains is eroded at different rates depending on the hardness of the rocks.

The landward edge of the coastal plain is known as the fall line. Waterfalls characterize it as rivers tumble over the edge of the mountains.

Coastal Plains Have Many Waterways

All rivers lead eventually to the ocean, and to do this, they must cross the coastal plain. Coastal plains are therefore characterized by a multitude of streams, rivers, and deltas, increasing the humidity of the area.

The high water availability in coastal plains allows for the growth of vegetation and the presence of fish and animals that need water for habitation. Swamps and marshes are common in coastal plains.

Deltas are seen in three different forms:

  1. Arcuate deltas have multiple tributaries which branch out radially.
  2. Cuspate deltas have a dominant V-shaped channel with curved sides.
  3. Bird’s foot deltas have long projecting distributaries that resemble a bird’s toes.
What Are The Characteristics Of Coastal Plains 01

Coastal Plains Have Fertile Soil

Deposition of silt, clay, sand, gravel, and vegetation results in rich soil high in humus and minerals. This gives rise to thick forests and areas of heavy vegetation.

In coastal plains characterized by erosion, there will be sandy soil, shingles, and large boulders that have fallen from cliff faces.

Coastal Plains Are Highly Populated

Historically people often settled on coastal plains due to fertile soil for agriculture. High rainfall is commonly associated with coastal areas making it an ideal region to grow crops and an easy place to farm.  

The Oxnard coastal plain in southern California is considered one of the most fertile places on earth. It is well known for strawberry farming, producing top-quality strawberries. 

Harbors, fishing, and sea trade also facilitated the population and urbanization on coastal plains. Due to the manner in which coastal plains develop, they are rich in natural resources, giving rise to multiple industries.

The flat land of coastal plains is easy to build on, and cities and towns developed in time. The result is that fifty to sixty percent of the world’s population currently live on coastal plains.

Dallas, Houston, Jacksonville, Denver, and Calgary are just a few examples of cities in the USA that are built on coastal plains.

Although it was advantageous for people to settle on coastal plains, it also made them vulnerable to natural disasters that include flooding such as tsunamis. An example was the Indian Ocean tsunami of December 26th in 2004 that flooded Phuket, Thailand.

Coastal Plains May Form Conservation Areas

Many coastal plains provide ideal conservation areas for wildlife reserves and parks. The rich vegetation and high rainfall allow the animals to thrive in these areas. Many plains promote the growth of forests, swamps, or wetlands, which facilitate the development of protected wildlife reserves.

The Arctic National Wildlife Refuge (ANWR) situated in Alaska is an example of a wildlife reserve on a coastal plain. 


Coastal plains are valuable regions for mineral resources and agriculture. They are bordered by the ocean and mountains and can be found on most continents throughout the world. They attract settlements, and cities built at coastal plain harbors are hubs of commerce and industry.