---
title: "Geological agent and features of running water"
subject: "Engineering Geology I"
chapter: 6
key: "semester_3/engineering_geology_i:geological-agent-and-features-of"
source: https://www.bctengineer.com/q/semester_3/engineering_geology_i/geological-agent-and-features-of
site: BCT Engineering
---

# Geological agent and features of running water

Engineering Geology I · Chapter 6: Physical Geology

- Asked in: 2081 Kartik (new course), 3 marks
- Video: [How Rivers Shape the Landscape: Crash Course Geography #23](https://www.youtube.com/watch?v=CDEj62HGNkk) — CrashCourse
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_3/engineering_geology_i/geological-agent-and-features-of
- Whole chapter: https://www.bctengineer.com/md/semester_3/engineering_geology_i/chapter-6

## Question

Define geological agent and discuss the geomorphic features produced by running water.

## Short answer

A geological agent is a natural force (e.g., running water) that erodes, transports and deposits material. Running water creates V-shaped valleys, gorges, waterfalls, potholes, meanders and terraces by erosion, and alluvial fans, floodplains, levees, point bars, braid bars, oxbow lakes and deltas by deposition.

## Answer

A **geological agent** is a natural force or medium (running water, wind, glacier, groundwater, sea waves and gravity) that erodes, transports and deposits earth material and so changes the surface.

#### Geomorphic features produced by running water
**Erosional work** of a river is done by hydraulic action, abrasion, attrition and solution. Features:

- **V-shaped valley:** formed by vertical (downward) cutting in the youth stage, in the hills.
- **Gorge and canyon:** deep, narrow valley in hard rock, e.g. the Kali Gandaki gorge.
- **Waterfall and rapids:** form where hard rock lies over soft rock; a plunge pool forms at the base.
- **Potholes:** circular holes drilled in the bed by swirling pebbles.
- **River terraces:** step-like old floodplain levels left after the river cuts down again.
- **Meanders and ox-bow lakes:** formed by lateral (side) cutting in the old stage.
- **Interlocking spurs:** ridges of the valley sides that project alternately into the winding valley of a young river.

**Depositional work** occurs when the velocity and carrying capacity fall (on gentle slopes, at the river mouth, and on the floodplain during floods). Features:

- **Alluvial fan:** cone-shaped deposit where a mountain stream meets a plain, e.g. the Bhabar zone at the foot of the Siwaliks.
- **Floodplain:** broad, flat valley floor built by flood deposits.
- **Natural levees:** low ridges of sand and coarse silt built along the banks during floods.
- **Braid bars and point bars:** sand and gravel bars in the channel (braid bars) and on the inner bank of bends (point bars).
- **Delta:** fan-shaped deposit at the river mouth, e.g. the Ganges-Brahmaputra delta.
- **Ox-bow lake and meander scars:** cut-off bends.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. A geological agent is:
   A. A natural force or medium that erodes, transports and deposits earth material
   B. A type of rock
   C. A mineral
   D. A fault
   Answer: A. Examples are running water, wind, glacier. (Key point: Definition)

2. Ox-bow lakes and meanders form by:
   A. Vertical cutting in youth
   B. Side cutting in the old stage
   C. Glacial plucking
   D. Wind abrasion
   Answer: B. Lateral erosion dominates in old age. (Key point: Ox-bow)

3. How do pot holes form?
   A. Collapse of caves
   B. Freezing
   C. Swirling pebbles drill circular holes in the bed
   D. Wind blast
   Answer: C. They result from abrasion by swirling pebbles. (Key point: Potholes)

4. Where is a delta formed?
   A. In the hills
   B. In a gorge
   C. At the head of a glacier
   D. At the river mouth where velocity and load capacity fall
   Answer: D. Deposition builds a fan-shaped deposit. (Key point: Delta)

## Related in Engineering Geology I

- [Geological work of running water and its landforms](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Ageological-work-of-running-water) — Engineering Geology I, chapter 6, asked 5×
- [Erosional feature of running water and wind](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Aerosional-feature-of-running-water) — Engineering Geology I, chapter 6
- [Erosional features of glacier and underground water](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Aerosional-features-of-glacier-and) — Engineering Geology I, chapter 6
- [Erosional features of underground water](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Aerosional-features-of-underground-water) — Engineering Geology I, chapter 6