Exploring the Effect of Rainfall Variability and Water Extent in Tanguar Haor, Sunamganj
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Australian Journal of Engineering and Innovative Technology, 2(4), 66-76, 2020 Publisher homepage: www.universepg.com, ISSN: 2663-7804 (Online) & 2663-7790 (Print) https://doi.org/10.34104/ajeit.020.066076 Australian Journal of Engineering and Innovative Technology Journal homepage: www.universepg.com/journal/ajeit Exploring the Effect of Rainfall Variability and Water Extent in Tanguar Haor, Sunamganj Ripon Bagchi1*, Md. Alim Miah2, Papri Hazra3, Robiul Hasan4, Himadree Shekhar Mondal5, and Sujan Kumar Paul6 1Dept. of Disaster Risk Management, Patuakhali Science and Technology University, Dumki, Patuakhali, Bangladesh; 2Dept. of Environmental Science and Engineering, Jatiya Kabi Kazi Nazrul Islam University, Trishal, Mymensingh, Bangladesh; 3Dept. of Environmental Science, Patuakhali Science and Technology University, Dumki, Patuakhali, Bangladesh; 4Centre for Disability in Development (CDD), Dhaka, Bangladesh; 5An Organization for Socio-Economic Development (AOSED), Khulna, Bangladesh; and 6Dept. of Chemistry, Govt. P.C. College, Bagerhat, Bangladesh. *Correspondence: [email protected] ABSTRACT Tanguar haor is located in the north-eastern region of Bangladesh and frequently experienced extreme events such as high rainfall that affect the haor basin area with flash floods on a regular basis. Tanguar haor is usually foreseen to severe disastrous conditions for the reason of changes in rainfall patterns and water extent. The study was conducted at Tanguar haor of Sunamganj district. This study mainly focuses on the year to year rainfall variability (2001-2018) and water extent (2002-2018) in the Tanguar haor area. The specific objective of the study was to explore the effect of rainfall variability and water extent in Tanguar haor. Information and data were collected mainly from secondary sources. Analysis of data and assess the ecological effect of changes in rainfall patterns and water extent were the main activities of the study along with others. The findings of the study were changeability in rainfall patterns and water extent frequently caused a flash flood in pre-monsoon and monsoon season in the Tanguar haor area. Flash flood causes a vast amount of financial loss for the living people of the Tanguar haor that makes them more vulnerable to live well. The result of this study may help to gather new knowledge on the consequences of rainfall variability and water extent in the haor basin area. It may add the significance for the management of flash flood and severe stress in haor basin area. Keywords: Tanguar haor, Rainfall variability, Water extent, Flash flood, Analysis, Impact, and Flash flood. INTRODUCTION: approximately 19.37 million of people (BHWDB, Bangladesh with an area of 147,570 sq. km that lies 2012). Haor areas are generally featured as bowl- between 20°34'-26°38' N, and 88°01'-92°41' E shaped large tectonic depressions and receive large (Rashid, 1991). Bangladesh is widely recognized as amount of surface runoff water by rivers, khals and one of the most climate vulnerable countries in the become very extensive water body in the monsoon world. Haor basin area situated in north-eastern part but dries up mostly in the post-monsoon period usually characterizes with large to medium flood (Bevanger et al., 2001; and IUCN, 2002). Now-a- plain depressions (Sara et al., 2013). Hydro- days Bangladesh predicted as most vulnerable ecological features of haor basin area are flood plain country due to climate change (rainfall and water and marshy lands covered approximately 1.99 extent) particularly in haor basin area on account million hectares of area and accommodating of geographic location, feature of flood plains, UniversePG l www.universepg.com 66 Bagchi et al., / Australian Journal of Engineering and Innovative Technology, 2(4), 66-76, 2020 growing density of population, extreme poverty and water flow from the upstream point and regional very high dependency on the natural resources rainfall acted as an auxiliary factor which accelerates (Rahaman et al., 2014). Covering 9,727 hectares, the situation to be worst. During the month of Tanguar haor in north-east part of Bangladesh, November to February the Tanguar haor area adjacent to the Indian border, is part of wetland of experiences low rainfall and water extent, March to the Surma-Kushiyara rivers basins (BHWDB, 2012). May experiences medium or average rainfall and water extent and in the month of April to September Nowadays the variability of climatic parameter has the experiences high rainfall variability and water become a challenging issue. Tanguar haor (eco- extent. Due to heavy rainfall the study area usually system, livelihoods, and living people) are especially experiences flood in monsoon season but, sometimes sensitive to the different natural disasters including during pre-monsoon season heavy rainfall and flash flood, drought and storm surges (Munasinghe, streams from mountains area raises the water level of 2000). Rainfall as well as temperature is two major bounded rivers that flows to the haor basins and climatic variables that structured the socio- causes flash flood in the Tanguar haor of ecological system (Klain, 1998). Any change in Sunamganj. Northern parts and the eastern parts of rainfall pattern and temperature cycle and water Bangladesh usually affects by the extent of flash extent as a result of climate change caused flash floods. A flash flood is considered with the high flood in Tanguar haor (Elahi, 1988). Climatic feature rises of water level of rivers and subsequent of Tanguar haor are subtropical monsoon nature with overbank discharge with very high velocity due to three dominating seasons likely summer, monsoon high rainfall. In Tanguar hoar area, flash flood arises and winter. Summer is from April to June and after math of heavy rainfall, rises of water level in temperature ranges from 30.9 to 33.4 degree celsius. the Surma River and heavy inundation in the Winter is from October to February and temperature adjacent hills and mountains. These floods often ranges from 8.5 to 16.6 degree celsius (Rahaman et destroy the standing crops at the ripening stage and al., 2014). Average annual rainfall is 8000 mm in cause severe damages to the physical infrastructures northern part of Sunamganj. Within Sylhet region along haor basin area (Saju et al., 2020). out of total annual rainfall 65-69% rainfall occurs in summer. The spring experiences with 21-23% of Considering all of these issues this study focuses on annual rainfall and the autumn experiences with 6- the variability in rainfall pattern and water extent in 8% of annual rainfall (Rahaman et al., 2014). High Tanguar haor area. The specific objectives of the rainfall during pre-monsoon season causes flash study were as follows: (i) to analyze major climate flood in haor area (Munasinghe, 2000). change parameters (rainfall, water level); (ii) to find out the effect of rainfall variability and water extent Tanguar haor in Sunamganj district of Sylhet in the study area; (iii) to follow up some measures division experiences high variability in rainfall and for the management of flash flood in Tanguar haor water extent on a regular basis. This causes flash area. This study may help to reveal the actual flood event more severe in the Tanguar haor. During scenario and to take practical actions for the low water level the haor area experiences drought management of flash flood and ecological balance in condition but very less in average. Due to climate the haor basin area. change, high population density, environmental degradation causes several natural disasters in haor MATERIALS AND METHODS: area. But flash flood event are more frequent in this Selection of the Study Area - The study was condu- area rather than others. There has been relatively cted at Dharmapasha and Tahirpur upazilas of little scientific research characterizing the variability Sunamganj District in Bangladesh. Sunamganj is in rainfall and water extent as outcomes of flood situated in the Sylhet division with the Sylhet district hazards and similarly, little social science research adjacent to east, Habiganj district in south and targeting how vulnerable populations perceive to Netrokona district in west (Siddiqi, 2012). The flood risks through mitigation strategies. Rainfall is Surma, Kushiyara and Danuka river go through the one the major determinants of flood severity in district where as the Ratna River crossed the Sunam- Bangladesh especially in the haor basin area. Recent ganj district. Sunamganj has a maximum of 33.2 floods have turned into catastrophe due to huge degree celsius and a minimum 13.6 degree celsius UniversePG l www.universepg.com 67 Bagchi et al., / Australian Journal of Engineering and Innovative Technology, 2(4), 66-76, 2020 annual average temperature with annual rainfall of Climate change parameter (rainfall, water level) 3334 mm (Ashfaq, 2012). There are many haor and data in Tanguar haor - From Climate Change beel (wetlands ecosystems) in Sunamganj. Tanguar Knowledge Portal and IUCN, the collected data on haor in Sunamganj district has particular wetland rainfall (2001-2018), and water level (2002-2018) ecosystem of countrywide importance and already for this study are as follows and shown in Table 1. came into international focus with the international recognition as Ramsar sites and world heritage by Table 1: Climate change parameter data with periods of records in Tanguar haor area. UNESCO. Geographical position of Tanguar haor is at 25°06’ to 25°11’ N and 91°01’ to 91°06’ E. The Data