ANALYSIS OF SPATIAL DISTRIBUTION OF LANDSLIDES IN RATNAPURA DISTRICT SRI LANKA

Abstract

AttachedSri Lankan b asem en t con sists o f m ain ly m etam orphic rocks, w h ich accounts for 90 percent o f the total m ass. U n con solid ated sedim ents in the lo w ly in g areas and river v a lley s are o f recent origin, m o stly th ey have b een dated to the quaternary period. L andslides in Sri L anka h ave not far been defined, cla ssified and docum ented w ith in any standardized fram ew ork o f uniform ly understood and acceptable classification system s. B u t m ovem en t o f sedim ents is on e o f the fundam ental geom orp h ic p rocesses on the earth’s surface, w h ich occurs from on e landscape to the other. Precipitation slop e angle and so il depth are the m ain factors affectin g the lan d slid e p rocess. In addition to th ese, p h ysical factors such as so il type, rock type, g eo lo g ic a l structure, vegetation cover and various hum an factors affect this lan d slid e p rocess. N ation al B u ild in g R esearch O rganization (N B R O ), Sri Lanka has id en tified six causative factors inducing landslides as; bedrock g e o lo g y , hyd rology and drainage, surface overburden, slop angle range, land u se and land form s. The h yd rology and drainage and land u se can be id en tified as m ajor controllable and dynam ic factors am ong ab ove factors. T h ese factors should b e obtained tim e b y tim e to generate the landslide susceptibility potential m ap. N e a r ly 12,5 0 0 sq.km o f area spread over the districts o f N uw ara E liya, B adulla, K andy, Ratnapura, M atale a n d . Kaluthara seem s to b e h igh ly prone to land slid in g and m ass w asting. L an d slid es occurred in m any areas o f Ratnapura district, such as Ratnapura, P elm adulla, K alaw ana, N ivith igala and K ahaw atta D S d ivision s. T w en ty Grama S ew a N iladhari (G S N ) D iv isio n s w ere affected b y landslides. A ccord in g to in vestigation s carried out b y N B R O , there are 135 high-risk areas, 69 m edium risk areas and 67 lo w risk areas in the w h o le o f Ratnapura D istrict. T he m ain objective is to analyze the spatial distribution patterns o f landslide in Ratnapura district o f Sri L anka from a g eo lo g ica l perspective. S o the n ecessity o f a m eth od ology to co llect land u se data b y a rem ote sen sin g m ethod is em erged. T he m ethods that have been applied in data co llectio n , and an alysis.T his research introduces a m eth od ology to generate a landslide su scep tib ility potential m ap w ith the aid o f land u se data co llected b y u sin g rem ote sen sin g and G IStechniques.T he research m ain fin d out is d ev elo p ed a n ew landslide hazard vulnerability m ap and id en tified relationship b etw een lan d slid es and different factors.