Sains Ma1aysiana 28: 69-86 (1999)                                                                                                       Sains Bumi/

                                                                                                                                                                       Earth Science

The Application of Landslide Potential Hazard

Zonation Mapping in the Ebbw Valley,

Gwent, Wales, United Kingdom

Zulfahmi Ali Rahman

Program Sains Sekitaran

Fakulti Sains Sumber Alam

Universiti Kebangsaan Malaysia

43600 UKM Bangi, Selangor D.E. Malaysia

ABSTRACT

The application of landslide potential hazard zonation mapping in the study area is based on the successful application of this method used in the Rhondda Valley which is also facing landsliding problems. This method involves dividing of the study area into square grids 100 ´ 100 m² representing basic mapping and analyzing unit. The contributory factors of the slope instability were considered in preparing the potential landslide hazard map and being given an appropriate rating value. In this study, three main contributing factors were used for analysis: a slope angle, superficial deposit types and groundwater potential. This study indicates that most of the landslide areas are concentrated on the valley side and are largely triggered by the presence of human activity which also has altered the groundwater condition and surficial morphology. The landslide potential (LP) values were divided into two major categories including ‘areas with little landslip potential’(0 - 110 and 110 - 210) and ‘areas with some landslip potential’ 210 - 410 and 410 - 1200). According to this analysis, the minimal LP category occupies 54% of the study area then followed by high LP (17%). Meanwhile the slight and moderate LP categories represent 14% and 15% of the study area, respectively.

ABSTRAK

Penggunaan kaedah pemetaan pengezonan potensi bencana tanah runtuh di kawasan kajian berdasarkan kejayaan penggunaan teknik ini di kawasan Lembah Rhondda yang turut mengalami masalah kegagalan cerun. Kaedah ini melibatkan pembahagian kawasan kajian kepada grid keluasan 100 ´ 100 m² bagi mewakili unit asas pemetaan dan analisis. Faktor-faktor penyumbang bagi ketidakstabilan cerun dipertimbangkan dalam penyediaan peta pengezonan potensi bencana tanah runtuh dan didasarkan kepada nilai pemberat (rating) tertentu. Tiga faktor penyebab kegagalan cerun telah dipertimbangkan bagi analisis : sudut cerun, jenis endapan permukaan dan potensi air bawah tanah. Kajian menunjukkan bahawa cerun cenderung gagal tertumpu pada cerun lembah yang berkaitan dengan aktiviti manusia yang melibatkan perubahan keadaan air tanah semulajadi dan morfologi permukaan. Nilai potensi cerun gagal (LP) dibahagikan kepada dua kategori iaitu ‘kawasan dengan sedikit potensi cerun gagal’ (0 - 110 dan 110 - 210) dan ‘kawasan dengan sebahagian potensi cerun gagal’ (210 - 410 dan 410 - 1200). Berdasarkan analisis, kategori minima LP mewakili 54% daripada kawasan kajian dan diikuti oleh kelas maksima LP (17%). Manakala bagi LP sederhana kecil dan pertengahan masing-masing mewakili 14% dan 15% daripada kawasan kajian.

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