---
title: "Landslide versus debris flow"
subject: "Engineering Geology II"
chapter: 5
key: "semester_4/engineering_geology_ii:landslide-vs-debris-flow"
source: https://www.bctengineer.com/q/semester_4/engineering_geology_ii/landslide-vs-debris-flow
site: BCT Engineering
---

# Landslide versus debris flow

Engineering Geology II · Chapter 5: Geological Hazards

- Asked in: 2070 Magh, 2 marks; 2078 Baisakh, 1 marks (asked 2 times)
- Video: [Mass Wasting vs. Landslide: The Interesting Differences You Must Know](https://www.youtube.com/watch?v=h0ScbJpUiIk) — Geotourism and Modern Geotechniques
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_4/engineering_geology_ii/landslide-vs-debris-flow
- Whole chapter: https://www.bctengineer.com/md/semester_4/engineering_geology_ii/chapter-5

## Question

Differentiate between landslide (slope failure) and debris flow.

## Short answer

In a landslide, material slides or falls as a block on a slip surface with low to medium water content, speed slow to rapid. A debris flow moves like a viscous fluid, very rapid and saturated, following channels and depositing fans far downvalley.

## Answer

| Point | Landslide (slope failure) | Debris flow |
|---|---|---|
| Movement | Mass slides or falls as a block along a slip surface | Mass flows like a viscous fluid |
| Water content | Low to medium | Very high, saturated |
| Material | Rock, soil or debris | Mixture of mud, boulders and water |
| Speed | Slow to rapid | Very rapid |
| Path | Short, on the slope | Long, follows channels or gullies |
| Slope | Steep to moderate | Steep channel, gentle fan deposit |
| Trigger | Rain, earthquake, cutting | Intense rainfall, GLOF, landslide dam failure |
| Deposit | Near the source | Fan or levees far down the valley |

## Check yourself

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

1. How does debris flow move?
   A. As a rigid block along a slip surface
   B. By free fall
   C. By slow creep only
   D. Like a viscous fluid
   Answer: D. Debris flow is a mixture of mud, boulders and water flowing like a fluid. (Key point: Movement)

2. Which has very high water content and is saturated?
   A. Debris flow
   B. Rock fall
   C. Landslide
   D. Topple
   Answer: A. Landslides have low to medium water content. (Key point: Water content)

3. Where does debris flow material deposit?
   A. Inside the head
   B. As fan or levees far down the valley
   C. Near the source on the slope
   D. At the crown
   Answer: B. Landslide deposits remain near the source. (Key point: Deposit)

## Related in Engineering Geology II

- [Conditions for plane failure](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Aplane-failure-conditions) — Engineering Geology II, chapter 6, asked 2×
- [Failure mode: HS 75/230, BP 68/045](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Afailure-mode-hs75-230-figure) — Engineering Geology II, chapter 6
- [Failure mode: HS N45E/70, bedding N55E/45](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Afailure-mode-hs-n45e-70) — Engineering Geology II, chapter 6
- [Cut slope design: N41W/56 hillslope](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Acut-slope-n41w-56) — Engineering Geology II, chapter 6
- [Cut slope design: limestone N48E/52](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Acut-slope-limestone-n48e-52) — Engineering Geology II, chapter 6
- [Cut slope design: quartzite N55W/50](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Acut-slope-quartzite-n55w-50) — Engineering Geology II, chapter 6

## Related in other subjects

- [Landslide versus debris flow](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Alandslide-versus-debris-flow) — Engineering Geology I, chapter 6
- [Landslide versus slope failure](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Alandslide-versus-slope-failure) — Engineering Geology I, chapter 6
- [Short note: Debris flow](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Ashort-note-debris-flow) — Engineering Geology I, chapter 6
- [Causes of slope failure](https://www.bctengineer.com/question.md?key=semester_4%2Fsoil_mechanics%3Aslope-failure-causes) — Soil Mechanics, chapter 11, asked 4×