---
title: "Relative hazard"
subject: "Engineering Geology II"
chapter: 5
key: "semester_4/engineering_geology_ii:relative-hazard"
source: https://www.bctengineer.com/q/semester_4/engineering_geology_ii/relative-hazard
site: BCT Engineering
---

# Relative hazard

Engineering Geology II · Chapter 5: Geological Hazards

- Asked in: 2075 Baisakh, 2 marks
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_4/engineering_geology_ii/relative-hazard
- Whole chapter: https://www.bctengineer.com/md/semester_4/engineering_geology_ii/chapter-5

## Question

Describe relative hazard.

## Short answer

Relative hazard ranks areas by degree of hazard compared to each other, without absolute probability. It assigns weighted ratings to causative factor classes (slope, lithology, etc.), overlays them in GIS to derive a hazard index, and zones the region from very low to very high hazard.

## Answer

**Relative hazard** assessment ranks the different parts of a region according to their degree of hazard, **relative to one another**, without giving the exact probability or time of occurrence. It answers "which area is more hazardous?" rather than "how likely is the event?".

#### Method
1. Choose the causative factors (slope, lithology, structure, land use, rainfall, distance to faults and streams, landslide inventory).
2. Give each factor class a rating or weight (rating of low, moderate, high).
3. Overlay the maps (GIS) and add the weighted values to give a hazard index.
4. Divide the region into zones: very low, low, moderate, high, very high.

#### Uses
- Regional planning and land-use zoning.
- Priority for detailed investigation and mitigation.
- Quick, cheap hazard maps when data are limited.

It is qualitative or semi-quantitative, subjective, and not suitable for exact design.

## Check yourself

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

1. What question does relative hazard answer?
   A. What is the factor of safety?
   B. Which area is more hazardous?
   C. How likely is the event in a year?
   D. What is the exact time of occurrence?
   Answer: B. It ranks areas against one another. (Key point: Question answered)

2. How is a hazard index obtained?
   A. Calculating return period
   B. Core drilling
   C. Weighting factor ratings and overlaying maps in GIS
   D. Computing the factor of safety
   Answer: C. Weighted factor maps are added to give an index and zones. (Key point: Method)

3. What is a limitation of relative hazard?
   A. Needs exact probability
   B. Is fully quantitative
   C. Is expensive
   D. Subjective and unsuitable for exact design
   Answer: D. It is qualitative or semi-quantitative. (Key point: Limitation)