Potensi banjir (genangan) di Kotamadya Mataram: (Suatu kajian berdasarkan perspektif kelingkungan)

Gulam Abbas, Dr. Karmono Mangunsukardjo, M.Sc.

1997 | Tesis | S2 Ilmu Lingkungan

INTISARI Penelitian ini bertujuan mengkaji potensi banjir (genangan) di wilayah Kotamadya Mataram ditinjau dari karakteristik lahan (kondisi fisik lingkungan) dan ke- adaan perubahan penggunaan lahan (perkembangan area ter- bangun) karena pertambahan jumlah penduduk. Penentuan karakteristik lahan dalam hubungan dengan banjir (genangan) menggunakan metode deskriptif kualita- tatif. Penentuan hubungan pertambahan jumlah penduduk, peningkatan luas area terbangun dan banjir (genangan) menggunakan analisis keruangan dan analisis regresi. Analisis regresi digunakan untuk mengetahui pengaruh pertambahan jumlah penduduk terhadap luas area terbangun dan untuk mengetahui pengaruh peningkatan luas area ter- bangun dan pertambahan jumlah penduduk terhadap area banjir (genangan). Hasil penelitian menunjukkan bahwa karakteristik lahan yang berkontribusi terhadap banjir (genangan) se- bagai berikut: topografi (relief) sebagian besar wilayah adalah datar (flat land), kemiringan lahan 0-2%; permu- kaan airtanah tergolong dangkal (berkisar 1,0-6.0 me- ter), sungai-sungai induk seluruhnya bermeander, lereng bagian hilir berkisar 3%, muara sungai kerapkali tertu- tup pasir pantai, lahan miskin anak sungai (drainase alam buruk); dan kondisi curah hujan cukup tinggi. Analisis keruangan menunjukkan bahwa di seluruh da- erah penelitian, pada periode pertama (1975-1985), per- sentase peningkatan kepadatan penduduk seimbang dengan peningkatan luas area terbangun (masing-masing 42,5% dan 45%), sedangkan persentase peningkatan luas banjir (ge- nangan) meningkat 141 %. Pada periode kedua (1985-1995), persentase dimaksud masih tetap berimbang (masing-masing 25,3% dan 23,8%), sedangkan persentase luas banjir me- ningkat 104%. Selain itu analisis keruangan memperlihat- kan perluasan area banjir (genangan) cenderung menuju ke arah Barat dan ke arah Selatan. Sementara pertambahan jumlah penduduk, perluasan area terbangun, dan perluasan area banjir (genangan) cenderung terpusat pada wilayah yang sama. Analisis regresi menunjukkan bahwa pertambahan jum- lah penduduk mengakibatkan peningkatan luas area terba- ngun, yakni tiap-tiap pertambahan satu penduduk akan me- ningkatkan area terbangun seluas 10,85 m. Sementara pe- ningkatan luas area terbangun dan pertambahan jumlah penduduk tidak menunjukkan adanya pola hubungan linier terhadap luas area banjir (genangan).

ABSTRACT The aim of this study was to examine the potential of flooding (inundation) in Mataram Municipality, ob- served from land characteristics (the physical environ- mental conditions) and the land use changes (the exten- sion of the built up area), due to population increase. In order to determine land characteristics which are related with flooding (inundation), the qualitative descriptive method was used. In order to determine the relationship between population increase, extension of the built up area and flooding (inundation), spatial and regression analysis were used. Regression analysis was used to determine the influence of population increase towards the extension of the built up area, and to determine the influence of extension of the built up area and the increase in population towards flooding (inundation). Result of the study indicated that the land charac- teristics that contributes towards flooding (inundation) are: topography (relief) of the area which is generally flat, slope steepness of the land wich is between 0 - 2%; the area has shallow groundwater (1.0 6.0 meters), the major rivers meanders, the lower slope of the rivers are more or less than 3%, the rivers mouth are often blocked by the sand, the area has no tribu- taries (poor drainage); and high amount of rainfall. The spatial analysis indicated that in the entire study area, during the first period (1975-1985), the percentage increase in population density was in balance with the extension of the built up area (42,5% and 45% resfectively), while the percentage extention in flood- ing (inundation) was 141%. During the second period (1985-1995), the percentage increase was in balance (25,3% and 23,8% resfectively), but the percentage in- crease in flooding area was 104%. Besides that it also indicated that the direction of flooding extension tends towards the West and South. Increase in the total number of people, extension of the built up area and extension of flooding tends to concentrate in the same area. Regression analysis indicated that population in- crease caused an extension in the built up area, that is; every increase by a single person was followed by an extension in the built up area of about 10.85 m2. While an extension in the built up area and increase in popu- lation did not indicate any significant influence on the flooding area.

Kata Kunci : Potensi Banjir, Genangan, Perspektif Lingkungan, Kotamadya Mataram