A Rainfall Intensity-Duration Threshold for Mass Movement in Badulla, Sri Lanka

Abstract

Mass movement in Sri Lanka is mainly triggered by heavy rainfall. International literature is rich of works defining rainfall intensity-duration models to identify the rainfall threshold for various types of Mass movement. However, studies have not focused to establish a relationship between intensity and duration of rainfall in Sri Lanka. Therefore, this study focused to establish rainfall intensity-duration models to identify the rainfall threshold for mass movements in Badulla district in Sri Lanka, where forty four (44) rainfall events that resulted in same number of landslides during the last three decades were considered. Results indicate the rainfall threshold relationship fits to the log linear model of the exponential function, I = α·D −β . The constructed I-D curve revealed that short duration (<2 h) and high-intensity (>54 mm/h) in rainfall events can potentially trigger the landslide. However, long-duration (>8 h) and low-intensity (<25 mm/h) in rainfall events may also trigger mass movements in Badulla. As per the results, most mass movements occur during northeast monsoons and inter-monsoons. In general, higher mean rainfall intensities trigger the debris flows, while long-duration rainfall events can trigger both landslides and debris flow. When compared to Sri Lankan mass movements triggering threshold intensities are fairly higher than the global threshold values. It confirms that within Badulla, mass movements are triggered by very high intense and/or long duration rainfalls events only. Further, time series analysis of the rainfall events shows an upward trend of extreme rainfall events, which increased landslide occurring frequency in last six (6) years.

Altitudinal and temporal variation of surface water quality: An assessment in Badulu Oya Catchment, Sri Lanka

“…Available dominant rock types, crystallization process are the main factors that regulate the chemical composition and physical properties of surface water [14]. Badulu Oya catchment being located in the intermediate zone on the leeward side of Central Highlands receives an average 2000 mm comparatively low rainfall [15]. The catchment receives high rainfall during October to November and December to February second inter monsoon and during North East monsoon periods.…”

Untitled

“…Recovery was assumed as a function of emergency recovery (ER), infrastructure resettlement (IR) and long-term recovery (LtR). There might be several factors (performance Indicator) that could be assumed to affect in positive and negative mean on dependent variables of ER, IR and LtR as shown in Table 1 [4,8,14].…”

“…However, increase of frequency and severity of landslides in Sri Lanka, attention on landslide recovery becomes more significant and complicated [8]. The landslide recovery process is often long, costly and complex, and the responsibilities of the recovery project distributed among numerous sectors and stakeholders [9].…”

Participatory Landslide Inventory (PLI): An Online Tool for the Development of a Landslide Inventory

“…Studies conducted by the NBRO have revealed that nearly 70% of the landslides that occurred in populated areas in Sri Lanka are human-induced [4]. As a result, the frequency and severity of landslides in the country have increased in the recent past, which is in line with global trends [5][6][7]. Scientists therefore mostly focus on promoting landslide risk mitigation measures at local and global scales based on the available landslide information.…”