Flood adaptation strategies under climate change in Nepal: a socio-hydrological aalysis

Flood adaptation strategies under climate change in Nepal: a socio-hydrological aalysis

Abstract

While climate change is global in scale, developing countries and their people tend to suffer the earliest and the most because of their weak economies and low levels of resilience and adaptive capacity. Increases in the frequency and intensity of extreme events such as floods, droughts, fires, pests and diseases are creating tremendous challenges in natural and social systems. Because of the special climatologic characteristics, fragile topography, glacial melting and ever increasing deforestation rates, floods are a particular challenge to Nepal. It is likely that climate change will further exacerbate the problem as the frequency of high intensity rainfall is projected to increase, demanding special attention to flood mitigation and adaptation points of view.

The West Rapti river basin, lying in the mid-western part of Nepal, has the general characteristics of other major river basins in that country. This dissertation examines key elements of the West Rapti Basin as a socio-hydrological system in order to develop recommendations for flood mitigation and adaptation strategies. The specific objectives of this dissertation were to: (1) analyse hydro-climatic time series data and develop probable future climate scenarios for the West Rapti River basin, Nepal; (2) perform hydraulic modeling to assess flood inundation in the study area and develop a flood hazard map; and (3) analyse potential adaptation strategies.

These objectives were addressed through the integration of three forms of analysis: (1) Hydraulic modelling to determine flood return periods and prepared flood zoning and hazard mapping under four climate change induced flood scenarios (current case: Scenario I; flood of 2030: Scenario II; flood of 2070: Scenario III; and flood of 2100: scenario IV); (2) Economic estimation of the willingness to pay (WTP) for flood mitigation in different flood zones (critical, moderate and low flood prone) and the flood scenarios; and (3) Social assessment to identify potential impacts of flooding in the Basin and some of the possible adaptive responses and preferences of the local people in regard to these responses. In addition, the study examined how adaptation strategies may change over time with exposure to climate change scenarios in different flood prone zones.

For the hydraulic modelling, hydro-meteorological time series data enabled investigation of the change in flow-related statistics over time, while spatial data were used to represent the physical settings of the Basin. Contour and land use data were used for flood analysis at different return periods and hydraulic modeling was performed using HEC-RAS to simulate the hydraulic process of the Basin for preparing the flood hazard zones.

With regard to economic and social assessments, a multi-stage, multi-level and multi-stakeholder process was followed. Initially, in consultation with central level stakeholders by way of interviews and local level stakeholders through focus group discussions (FGDs). The FGDs were helpful in identifying and understanding pre-flood, during-flood and post-flood adaptation strategies, both at household and community levels, and pre-testing the semi-structured questionnaire for the household survey. This questionnaire was then administered through 240 randomly selected households from all flood zones and a range of socioeconomic backgrounds. In order to elicit information regarding appropriate adaption strategies and WTPs, flood maps of different flood scenarios were shown to all respondents. Finally, key academicians, civil society and government officials were briefed on the issues and priorities identified from the field level survey, and they were also interviewed for possible policy level interventions.

Analysis of meteorological data shows that the annual average temperature of the study area is increasing at a faster rate than the national (0.06ºC) and global average (0.03°C). Similarly, the intensity and magnitude of rainfall and thus floods is increasing. Similarly, the monsoon season is shifting more towards the currently defined „post-monsoon‟ season, highlighting a need to redefine the timing of the monsoon season and to identify appropriate crops, as well as planting and harvesting times for these. It is predicted that the area of critically hazardous flood zone will gradually increase under future flood scenarios.

The average WTP varied by flood hazard zone and, within the zone, by climate change-induced flood scenarios. The average WTP of respondents was highest for the critical flood prone zone, followed by the moderate and low flood prone zones. Similarly, within each zone, average WTP increased with increasingly divergent climate scenarios. As expected, for all scenarios, average annual crop income, livestock income and damage costs were highly positively correlated with average annual WTPs.

As floods are part of their life, local people have adopted various adaptation strategies, both at individual and community levels. At an individual or household level, “construction of drain to divert the floods”, “caring children, elderly people and releasing domesticated animals” and “managing household foods and martials” were the three most prioritised pre, during and post flood adaptation strategies, whereas at community level, “developing flood management plan”, “updating contact information” and “exchanging helps to each other” were perceived to be most important.

This study found that peoples‟ ways of thinking and their preferences for particular adaptation strategies changed with exposure to climate change scenarios. For example, a less sever flood scenario I, the simplest and least expensive form of adaptation strategy “bamboo mesh with sand filled bags” was most preferred; however, its perceived importance reduced with exposure to the more severe future flood scenarios. With exposure to an intense flood scenario, the most complex and expensive adaptation strategy “reservoir/flood regulating structures” emerged as the most preferred. The process and results of this study highlight two things: the importance of visual aids to understand the magnitude of floods impacts; and the value of information about projected flood levels and potential risk to enable people to choose appropriate adaptation strategies.

Furthermore, there is poor co-ordination between and within flood related government and non- governmental organisations in Nepal, and flood victims are getting little support from them. Local people are left alone to mitigate and adapt to flooding on their own. Many flood related committees, plans and actions have been initiated and maintained by flood affected people. However, this knowledge and these practices have not been scientifically validated, pointing to a need to address this issue; scientifically validated indigenous and local knowledge and skills have potential to become sustainable flood adaptation options.

This research bears special significance for the West Rapti River Basin as it provides field based evidence to policy makers and other key stakeholders to identify and prioritize areas for flood adaptation, to adopt appropriate policy and programs, and to allocate and justify scarce public and private resources. However, the overall approach and methodological framework for socio- hydrological analysis would be applicable in different parts of Nepal and developing countries, with similar bio-physical and socio-economic conditions and flood problems.