RE-DEMARCATION OF 'CONSERVATION AREAS' IN SRI LANKA BASED ON SOIL EROSION POTENTIAL

摘要

The Soil Conservation Act, No. 25 of 1951, provides the necessary legal framework to declare any area as "Conservation Areas". Declaration of "Conservation Areas" of Sri Lanka has been done mostly based on expert judgements and no comprehensive studyhas been undertaken for the purpose. Furthermore, the field situations suggest that there are instances where the areas that are highly vulnerable to soil erosion have been excluded from the declared "Conservation Areas". Therefore a study was carried out with the objective of identifying a geographical area within the Island which is sensitive in terms of soil erosion, and to recommend the said area to be declared as a "Conservation Area" under the Soil Conservation Act of Sri Lanka. Input parameters considered for the study were, erosivity of rainfall (R), the credibility of soil (K), the effect of slope length factor (Ls). The existing range of each input variables were grouped into ten classes and each class was given a rating within 1-10 based ontheir ranking in relation to soil erosion. Subsequently, an erosion index (El) was formulated which is an indicator of the relative potential for sol erosion. The El values were grouped into classes based on two classification methods and the result wasused to delineate erosion prone areas. The study justifies the necessity for re-demarcation of boundaries of "Conservation Areas" and demarcates boundaries in relation to the nearest district boundary, river, stream, road or trigonometric point. The landextent of the proposed boundary is approximatelylO, 618 sq. km or 16 % of the total landmass of Sri Lanka.