hazard assessment of kawache glof

Hazard Assessment of Kawache GLOF

Introduction:Episode occurred on 15th August, 2003 in the

upper reach of Madi river.Basic cause of GLOF linked with the important

meteorological parameter i.e. temperature.Methodology:Social SurveyFlood mark discharge measurement method

Findings: Social survey-Ethnicity dominated by gurung.Most witness the event with experience of-

event occurred at night with clear sky, producing foul smell, land shaking and large sound due collision of Boulders.

Desertification of fertile land, killing 5 people, deposition of large boulders, trees logs and soil debris.

Flood mark up to 5m.

Flood mark discharge measurement method-Suitable method for flood discharge

measurement. flood mark identified through local respondent.Flood discharge at chasu:-30161.43m3/secConclusion:Huge magnitude flood has cause huge loss of life

and property and also destabilized slope triggering cyclic landslide each year.

Monitoring of Temperature trend, detail assessment of life and property loss, study of Geomorphologic changes is necessary to develop useful models.

Landslide hazard mappingIntroduction:provide residents the information on the

range of possible damage and disaster prevention activities.

based on : slope gradient, slope aspect, elevation, slope shape, geology, land use, soil type, average annual rainfall, distance from a road, distance from a stream, distance from a geological structure and distance from a major ridge line (Paudyal and Dhital 2005).

Methods of Hazard mapping1. Digital Grid: Cumulation of rating at each grid Superimposing different maps with rated grid

sheet Generally, used PC software- SHIVA (wagner

et al. 1990)2. Line Hazard mapping: Subdivision of survey line into facets where

hazard rating is attributed. Can take narrow area but no Cumulation

done.

Study area:

Pokhara valley is a beautiful of natural paradise in western Nepal having Area of 200 sq km.

It extends between 25°7' and 28°10'N latitude.

83°50' and 84°50' E longitude

Pokhara valley are divisible into seven formations: Begnas, Siswa, Tallakot, Ghachok, Phewa, Pokhara and Rupakot Formations (Yamanaka et al., 1982).

Observations: A) Mapping parameters index;• Soil depth:- A(<1m), B(1-3m),C(3-6m) & D(+6m)• Vegetation:- 1-2-3-4-5 (no to dense vegetation

range) • Slope:- I-II-III-IV-V (Steep to gentle range)

S.N.

Reference site Slope Soil depth

Vegetation

Soil type Total rating

1. Sedi Bagar (800m)

Top colluvial II B 2 Residual 0.36

Alluvial (1) III C 2 Gravel, sand and silt 0.36

Alluvial (2) IV D 3 Sandy gravel, sand and silt

0.34

2. Chahadidada (798m) III C 2 Transported colluvial

0.4

3. Phyaureko Tudo (816m)

Colluvial fan I A 3 Active colluvial 0.23

Alluvial Fan III C 2 Non- active alluvial 1.34

4. Bhakunde Bagar (806m)

Colluvial fan II B 4 Sand and silt 0.35

Alluvial fan IV C 2 Sand, silt and gravel 0.33

5. Pame (794m)

Colluvial fan II B 3 Sand and silt 0.35

Alluvial fan III A 2 Sand silt and gravel 0.18

B) Hazard rating parameter values:

C) Recommended hazard level:S.N. Reference site Total rating Hazard level Range of

hazard

1. Sedi Bagar (800m)

Top colluvial 0.36 Medium Less than 0.30 (Low)

Alluvial (1) 0.36 Medium

Alluvial (2) 0.34 Medium

2. Chahadidada (798m) 0.4 Medium Between 0.31 & 0.60 (Medium)

3. Phyaureko Tudo (816m)

Colluvial fan 0.23 Medium

Alluvial Fan 1.34 Very high

4. Bhakunde Bagar(806 m)

Colluvial fan 0.35 Medium More than 0.90 (Very high)

Alluvial Fan 0.33 Medium

5. Pame (794m)

Colluvial fan 0.35 Medium

Alluvial Fan 0.18 Low

Conclusion:Hazard level is based on cumulative rating

grid system.Alluvial fan at Phyaureko Tudo showed very

high hazard level.Alluvial Fan at Pame showed low hazard level. Recommended hazard level here is based

upon only four parameters but for more reliable result, all parameters introduce above need to be assigned.

References:Deoja, B., Dhital, M., Thapa, B., and Wagner,

A. (Principal Editors), 1991, Mountain Risk Engineering Handbook. International Centre for Integrated Mountain Development, 574-618 p.

Paudyal, P., and Dhital M.R., Landslide hazard and risk zonation of Thankot- Chalnakhel area, central Nepal., Jour. Nepal Geol. Soc. V. 31, 43-50 p.