Water Induced Disaster Mitigation from Watershed Management Perspective in Nepal - an Example from Dobhan Khola Watershed, West Nepal
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Vol. 4 No. 1-3 INTERNATIONALPathak JOURNAL./Int. J. L OFsld. LANDSLIDE Env.(2016) 4 (1AND-3),1 ENVIRONMENT-8 Dec embe r 2 01 6 Water Induced Disaster Mitigation from Watershed Management Perspective in Nepal - An Example from Dobhan Khola Watershed, West Nepal Dinesh Pathak1 Central Department of Geology, Geodisaster Research Center, Tribhuvan University, Kathmandu, Nepal ORIGINAL ARTICLE CorrespondenceCorrespondence to:to: DineshDinesh Pathak Pathak CentCentralal Department Department of of Geology, Geology, Geodisaster Research Center, Tribhuvan University Email: Kathmandu, dpathaktu [email protected] Email: [email protected] Abstract Water induced disasters are common phenomenon in the mountainous region of the active Himalayan belt. It is the major cause of annual loss of lives and properties in Nepal. The water induced disaster management is generally carried out in basin, sub-basin or watershed level through watershed management approach. Exploration of water induced disaster and evaluation of appropriate watershed management in Dobhan watershed in Palpa district, west Nepal has been carried out. Water induced disaster events like landslide, bank cutting, flood and sediment transportation are common in the watershed. Around 20% of the Dobhan watershed is covered by agriculture land and majority of it is on the sloping terrace. Though more than 65% watershed area is covered by forest, there is significant encroachment leading to degradation of the forest area and natural condition of the forest. Watershed related information, like geology, geomorphology, river morphology, land use, socio-economic conditions of the people in the watershed are some of the factors to be considered in the watershed management leading towards water induced disaster risk reduction. This paper presents various parameters and approach required for watershed management of the Dobhan Khola watershed, which is equally important to deal with other watershed of the country in holistic manner for the mitigation of water induced disasters. Keywords: Water induced disaster, watershed management, watershed atlas, Dobhan Khola 1. Introduction and ethical perspective (Newson, 1992; Marty, 1997). Each perspective corresponds with one or more The mountainous region of Nepal is facing loss of lives scientific disciplines, and each highlights some and property each year due to the water induced aspects of RBM. Watershed is a small component of disaster. The water induced disasters are taking place river basin. due to general tendency of underestimating the natural phenomena through deteriorating the environmental Disaster mitigation activities is essential condition of the mountainous region. It has significant from various perspectives like protection of impact also to the downstream areas. It has close environment in terms of natural resources and bio- relationship with poverty alleviation, natural resource diversity, protection of infrastructures, forced migration, management and sustainable development. conflict resolution that has eventual impact to the livelihood of people. This can be achieved through a There well managed watershed with conservation of are several perspectives on river basin management downstream. This situation will eventually minimize the (RBM). Some important ones are natural-science, watershed degradation thereby supporting to reduce engineering, social optimization, legal, decision-making sediment deposition as well as floods in downstream 9 Water Induced Disaster Mitigation from Watershed Management Perspective in Nepal - An Example from Dobhan Khola Watershed, west Nepal Vol. 4 No. 1-3 Pathak./Int. J. Lsld. Env.(2016) 4(1-3),1-8 Dec embe r 2 01 6 2 which will eventually create a favorable condition for 96 km . The watershed is elongated in east west direction reducing the water induced disaster. A harmonic and lies in the Siwalik region of Palpa district in Western relationship will be maintained between nature and the Development Region (Fig. 1). The watershed consists of people. Within river basins, land and water, surface mainly 4 VDCs, namely Dobhan, Kachal, Baldengadhi water and groundwater, and water quantity and and Juthapauwa. water quality interact in many different ways (Mostert, 1999). To prevent overuse and degradation, prudent management is necessary that pays due attention to these interrelations. Watershed management has been the priority of government of Nepal that is primarily focused to conservation of soil, water and other biological components within the watershed. However, it has given low priority for disaster risk reduction. For example, the huge mass wasting (either in the form of landslide or debris flow) in the upper watersheds are usually affecting both the upstream as well as the downstream population. The event could be either from the overexploiting natural resources or purely a natural event. Therefore, watersheds need to be Figure 1 Location of Dobhan Khola watershed in western studied to identify the natural and human induced Nepal. The location of Nepal in the Himalayan range is shown causes for the disaster. It can be done through the in inset at top right corner. consideration of multi-layer components, multi-sectoral interaction and temporal information collection. The Dobhan Khola watershed is one of the most affected The watershed ones in the Tinau river basin. Water induced disasters management activities is typical in each watershed, resulting from severe cut banks, landslides and debris which should be identified through thorough study of flows are common in this area. There are a number of various factors. Educating people in the causes and shallow to deep-seated landslides developed due to toe consequences of various factors for water induced cutting by the Dobhan Khola. Likewise, the lower disaster, including proper land use practice, is necessary terraces of the Dobhan Khola are under a high flood to implement the activities. Water induced disasters in hazard. The Dobhan Bazar that lies near the confluence the Nepalese mountainous regions should be addressed of Dobhan Khola and Tinau River is at risk due to bank through the watershed management perspectives. cutting by the river. The rainfall data as measured in The aim of this paper is to Butwal meteorological station maintained by the explore various interlinked components to reduce water Department of Hydrology and Meteorology, Government induced disaster from the watershed management perspective. A typical watershed in the southern of Nepal has been analyzed (Fig. 2). This is the nearest meteorological station lying south of the study area. It is Himalaya region has been considered in the study to justify the various data and aspects to be considered to observed that the maximum annual rainfall was 3251.9 address the issue. The importance of satellite imageries mm in 1996 and the minimum was 1399.2 mm in 1998. forE PrelevantP of th edata ben cextraction,hmark mo dassessmentel (model 1)of landsharply use The 26 year average (1985-2010) being 2327 mm. The increasecondition,d as soon asevaluation the shaki nofg ehazardvent in itiandated vulnerability and then lev ehaveled maximum rainfall occurred between the months June to off. Whbeenile fo rcarried model 2out and in 3, the in wwatershedhich this loconsidered.cation was Variousin the September. parameters of the watershed to be considered for the water induced disaster mitigation activities are presented in the paper. The paper emphasizes on the necessity of dealing the entire watershed in a holistic manner for the reduction of water induced disaster. This approach of reducing the water induced disaster through watershed management perspective is supposed to be useful in other watershed in the Nepal Himalaya. 2. The study area Figure 2 Annual rainfall variation between 1985 and Dobhan Khola is one of the tributaries of approximately 2010 in the Butwal meteorological station. north south flowing Tinau River and covers an area of 10 Water Induced Disaster Mitigation from Watershed Management Perspective in Nepal - An Example from Dobhan Khola Watershed, west Nepal Vol. 4 No. 1-3 INTERNATIONALPathak JOURNAL./Int. J. L OFsld. LANDSLIDEEnv.(2016) 4(1 AND-3),1 -ENVIRONMENT8 Dec embe r 2 01 6 3. Geology of Dobhan Khola watershed area was digitized in GIS. This map consists of various geological formations with rock types and geological Though the watershed is distributed both in the Lesser structures. Likewise, the relevant documents were Himalaya in the north and Siwalik region in the south, collected from concerned organizations like Soil the present study is focused only in the Siwalik region Conservation and Watershed Management Field office, (Fig. 3). The Siwalik Group consists of fluvial deposits Water Induced Disaster Prevention Field Office, strongly influenced by the Neogene tectonics of the District Agriculture Development Office. Himalaya (Prakash et al. 1980). Rocks of Lower Siwalik (LS) and Middle Siwalik (MS) are distributed The primary in the area. The Lower Siwalik (LS) is characterized by data was basically extracted from the satellite imageries alternate beds of fine-grained sandstone, siltstone and and from field investigation. There is tremendous use of variegated mudstone. It is a mud and silt dominated the satellite imageries in watershed management. It is helpful right from the beginning of watershed sequence and is the oldest formation in the Siwalik management planning to execution stage. Various Group. The Middle Siwalik (MS) is characterized by information