Nepal Hazard Risk Assessment - Asia-Pacific Gateway for Disaster ...

More documents

Recommendations

Info

Nepal Hazard Risk Assessment 3 HAZARD ASSESSMENT 3.1 BACKGROUND Hazard assessment is essential and first step of risk assessment. Hazard assessment commonly shows zones of different intensity or probability of certain hazard. Hazard maps (BGR and GAI, 2009) can be applied in many ways: • It serves as information for the public about threats in their living environment • It can be used as input for land use, strategic and business planning • It is the basis for civil engineers, town planers for safe and sustainable development • It can work as the basis for developing risk transfer mechanism through insurance and catastrophic bonds etc. Practitioners broadly differentiate between “susceptibility” and hazard maps. Susceptibility maps(BGR and GAI, 2009) provide spatial information on whether a certain terrain is prone to the occurrence of a hazardous event. The term is particularly common for landslides studies, where static parameters such as topography / slope, soil condition and average rainfall can be used to indicate the potential for mass movements. A hazard map (BGR and GAI, 2009) additionally takes into account the temporal probability that a hazardous event may occur. For an example a flood hazard map is commonly based on the return period of river flooding levels. 3.1.1 CHARACTERISTICS OF HAZARD ASSESSMENT Hazard assessment is characterized by degree of severity, duration, extent of the impact area and their relationship. There are several ways by which, hazard assessment can be carried out. The comprehensiveness of hazard assessment depends on following factors: • Availability of disaster event data and geological, geomorphological, demographic data • Availability of time and resources • Type and characteristics of hazards • Application of hazard assessment to the end users. There are several ways by which, hazard assessment can be performed, which largely depending upon availability of data and scientific tools like map analysis, analysis of aerial photography and imagery, field reconnaissance, aerial reconnaissance, drilling, acoustic imagery and profiling, geophysical studies, computerized terrain analysis and instrumentation. 3.1.2 SCOPE OF HAZARD ASSESSMENT IN THE PROJECT a. Earthquake Hazard Assessment Earthquake hazard assessment has been carried out based on Modified Mescalli Intensity Scale. The Peak Ground Acceleration map developed by Department of Mines and Geology has formed the basis for earthquake zoning. The attenuation relationship has been developed based on Trifunac (Trifunac and Brady, 1975). Other methods like Wald (Wald et al., 1999) and Probabilistic seismic Hazard Assessment Map (PSHA) have been compared with developed hazard map, validated and finalized. The study proposes five zones of earthquake namely “Very High”, “Moderate High”, “High”, “Medium”, and “Low” severity. The earthquake hazard assessment maybe referred at Section 3.2 b. Landslide Hazard Assessment The developed landslide hazard maps are classified into rainfall and earthquake induced landslide hazard. The landslide hazard maps are categorized into high, medium, low, and negligible severity. The landslide hazards assessment may be referred at Section 3.3 c. Flood Hazard Assessment Floods occur regularly and affect broadly the central and southern region of Nepal. There are several perennial rivers, contributing regular floods like Bagmati, Rapti, Kamala, Kankai, Tinau, Karnali, Babai and Narayani etc. Floods from these rivers are result in major losses of life and other economic sectors. The study aimed to carry out desktop based flood hazard assessment for selected rivers. The hazard assessment has resulted in defining inundation area and depth using one dimesion model namely “HECRAS”. The Flood scenario has been developed for various return periods of 10 years, 25 years, 50 years, 100 years and 500 years. The flood hazard assessment is further cross checked with established and official data and information. A national level technical team is also been consulted while finalizing the flood hazard assessment maps. The flood hazard assessment may be referred at Section 3.4 d. Drought Hazard Assessment In recent past, drought has occurred frequently in the country. Due to climate changes, rapid degradation of environment, exploitation of natural resources, the drought situation has been aggravated. The drought hazard assessment has been carried out using well established tools i.e. Standard Precipitation Index (SPI) and Soil Moisture Index (SMI). The detail of drought hazard assessment may be referred at Section 3.5 e. Epidemics Hazard Assessment Under the study scope health hazards have been classified as diseases and outbreaks. The health hazard mapping includes Diarrhoea, Kalazaar, Hepatitis, Influenza, Typhoid, Acute Respiratory Infection, Malaria, Sexual Transmitted Infection, Filariasis, Gastroentri Tuberculosis, and Leprosy. For each disease and outbreak, Incidence index have been developed. Further trend analysis has been carried out to understand severity of the problems. The details of Epidemic hazard assessment may be referred at Section 3.6. 40
Nepal Hazard Risk Assessment 3.2 EARTHQUAKE HAZARD ASSESSMENT Nepal has witnessed several large scale earthquakes in past centuries. The Department of Mines and Geology has developed Peak Ground Acceleration map for the whole country (Pandey et al., 2002). The earthquake hazard maps have been developed in MMI scale. The MMI scale is one of the simple indicators for understanding the severity of earthquake hazards. 3.2.1 MAP CONTENT Earthquake hazard map has been developed in Modified Mercalli Intensity scale (MMI), which shows distribution of intensity throughout the country. The earthquake hazard maps have been prepared for several return periods i.e., 500, 250, 100, and 50 yr. • Epicentre maps of Nepal Himalaya from National Seismological Centre (NSC, 2005) 3.2.4 METHODOLOGY Simplified illustration of methodology can be referred in Figure 3.1. Peak ground acceleration map from Nepal DMG is extrapolated into more continuous manner that resulted as this study PGA. PSHA analysis is carried out for lower return period based on DMG parameters (Pandey et al., 2002). Average difference from 500 year return period PGA to lower return period PGAs is used for creating map of lower return period PGA. These PGAs are transformed to MMI value. The last step is zoning the MMI value into specifics zone which resulted in final maps. More detailed description of methodology can be referred in Annexure-1. 3.2.2 APPLICATION OF MAPS Earthquake hazard maps have been developed for whole Nepal. Earthquakes zones are overlaid with district boundary. These hazard maps are developed for several purposes, such as: • Earthquake hazard maps will be helpful for physical and infrastructural development in the country. The map will help the policymakers and decision makers to understand the severity of earthquake hazard and take necessary action to sustain the development through introducing necessary programs and measures. • Most important sectors like education, health, housing, lifelines and transportation need special attention for earthquake safety. The earthquake zones will provide fare understanding about expected performance of structures during earthquakes and necessary measures to protect the structures. • The zones will further help the local urban government to introduce and enforce building byelaws and building codes to protect the urban infrastructure. • The maps will help national and international NGOs to prioritize the disaster risk reduction strategies. 3.2.3 DATA AVAILABILITY FROM SOURCES Data used for producing maps are: • PGA (Peak Ground Acceleration) map from NGI (Norwegian Geotechnical Institute) (NGI, 2004) • Baseline seismic hazard map, which contain PGA (Peak Ground Acceleration) map and report developed by Nepal DMG (Pandey et al., 2002). Nepal Department of Mines and Geology (DMG) have developed probabilistic seismic hazard assessment (PSHA) for bedrock peak ground horizontal acceleration for five hundred return periods. • Earthquake catalog for Nepal area can be downloaded from USGS (USGS), that can be downloaded in http://earthquake.usgs.gov/earthquakes/eqarchives/epic/ Figure 3.1. Methodology for earthquake hazard mapping. 41
Page 1 and 2: Nepal Hazard Risk Assessment Nepal
Page 3 and 4: Nepal Hazard Risk Assessment 3.1 Ba
Page 5 and 6: Nepal Hazard Risk Assessment Figure
Page 7 and 8: Nepal Hazard Risk Assessment Name M
Page 9 and 10: Nepal Hazard Risk Assessment PREFAC
Page 11 and 12: Nepal Hazard Risk Assessment EXECUT
Page 13 and 14: Nepal Hazard Risk Assessment years,
Page 15 and 16: Nepal Hazard Risk Assessment 1 INTR
Page 17 and 18: Nepal Hazard Risk Assessment 1.6 SC
Page 19 and 20: Nepal Hazard Risk Assessment 2 BASE
Page 21 and 22: Nepal Hazard Risk Assessment The tr
Page 23 and 24: Nepal Hazard Risk Assessment 2.4 AD
Page 26 and 27: Nepal Hazard Risk Assessment 2.7 HE
Page 28 and 29: Nepal Hazard Risk Assessment 2.9 FI
Page 30 and 31: Nepal Hazard Risk Assessment 2.10.3
Page 32 and 33: Nepal Hazard Risk Assessment 2.12 T
Page 34 and 35: Nepal Hazard Risk Assessment 2.14 P
Page 36 and 37: Nepal Hazard Risk Assessment 2.16 M
Page 38 and 39: Nepal Hazard Risk Assessment 2.18 G
Page 44 and 45: Nepal Hazard Risk Assessment On 50
Page 50 and 51: Nepal Hazard Risk Assessment 3.3 LA
Page 52 and 53: Nepal Hazard Risk Assessment • So
Page 56 and 57: Nepal Hazard Risk Assessment ‐ Ex
Page 70 and 71: Nepal Hazard Risk Assessment 30 30
Page 72 and 73: Nepal Hazard Risk Assessment (a) (b
Page 74 and 75: Nepal Hazard Risk Assessment % of s
Page 76 and 77: Nepal Hazard Risk Assessment 3.6 EP
Page 78 and 79: Nepal Hazard Risk Assessment Demogr
Page 86 and 87: Nepal Hazard Risk Assessment 3.7 AP
Page 90 and 91:
Nepal Hazard Risk Assessment REFERE
Page 92 and 93:
Nepal Hazard Risk Assessment Annexu
Page 94 and 95:
Nepal Hazard Risk Assessment Note:
Page 96 and 97:
Nepal Hazard Risk Assessment On the
Page 98 and 99:
Nepal Hazard Risk Assessment 1.2.7
Page 100 and 101:
Nepal Hazard Risk Assessment 2 ANNE
Page 102 and 103:
Nepal Hazard Risk Assessment 2.3 RE
Page 104 and 105:
Nepal Hazard Risk Assessment 2.4 MO
Page 106 and 107:
Nepal Hazard Risk Assessment 3 ANNE
Page 108 and 109:
Nepal Hazard Risk Assessment Extrem
Page 110 and 111:
Nepal Hazard Risk Assessment No Sta
Page 112 and 113:
Nepal Hazard Risk Assessment Premon
Page 114:
Nepal Hazard Risk Assessment (a) (b
show all

Nepal Hazard Risk Assessment - Asia-Pacific Gateway for Disaster ...

Create successful ePaper yourself

Delete template?

Save as template?