As a river approaches the sea and its flow velocity decreases, it often breaks up into several smaller channels. These branching streams are called what?

Introduction / Context:
In fluvial geomorphology, understanding how rivers behave near their mouths is essential. Many large rivers slow down as they enter coastal plains and eventually the sea, causing them to deposit sediments and split into multiple channels. These features are characteristic of deltaic environments and are described using specific terminology. This question tests whether you can correctly identify the term for such branching streams.

Given Data / Assumptions:

• The situation described is a river nearing the sea, losing speed, and breaking into multiple channels.
• Options provided are plateau, isthmus, peninsula, and distributaries.
• We assume standard definitions from physical geography.
• The focus is on river channels, not landforms such as types of land masses.

Concept / Approach:
When a river approaches its mouth and starts depositing sediments, it may split into several smaller channels, each carrying a portion of the flow. These are called distributaries, because they distribute the river's water and sediment load over a broader area of the delta. Terms like plateau, isthmus, and peninsula refer to landform categories, not to river channels, so they can be eliminated by concept.

Step-by-Step Solution:
Step 1: Identify that the question talks about the river breaking into smaller channels near the sea. Step 2: Recall that in a delta, a main river channel splits into several branches that fan out. Step 3: These branches are called distributaries because they distribute water away from the main channel. Step 4: Recognise that plateau refers to an elevated flat terrain, which is unrelated to this process. Step 5: An isthmus is a narrow strip of land connecting two larger land areas, again not connected to river branching. Step 6: A peninsula is a landmass surrounded by water on three sides, not a river channel. Step 7: Therefore, the only term matching the process is distributaries.

Verification / Alternative check:
Look at classic examples such as the Ganga Brahmaputra delta or the Nile delta. In both cases, the main river divides into several smaller river branches near the sea, and atlases or geography texts label these branches as distributaries. None of the other options would be used in those diagrams, which confirms that distributaries is the correct technical term.

Why Other Options Are Wrong:
Plateau denotes a high, flat region, often bounded by steep slopes, and has nothing to do with river mouths. An isthmus is a neck of land linking two larger land bodies, primarily a coastal landform. A peninsula is a landform extending into water, surrounded by water on most sides. These three options describe types of land areas and not river channels or flow patterns, so they do not fit the description in the question.

Common Pitfalls:
Some learners may be unfamiliar with the word distributaries and might confuse it with the better known term tributaries, which are streams that join a main river. Here, however, water is leaving the main channel, not entering it. Remember that tributaries bring water into a river, while distributaries branch off from the main river near its mouth. Keeping this difference clear prevents misinterpretation.

Final Answer:
The smaller channels formed when a river breaks up near its mouth and spreads out toward the sea are called distributaries.