MORFOMETRI DAS DAN APLIKASINYA UNTUK MENGETAHUI KARAKTERISTIK DAN STADIUM EROSI SUBDAS CIWIDEY, KABUPATEN BANDUNG, PROVINSI JAWA BARAT
| Main Author: | A, Maulana Mario |
|---|---|
| Format: | bachelorthesis doc-type Bachelors |
| Bahasa: | ind |
| Terbitan: |
, 2014
|
| Online Access: |
http://repository.unpad.ac.id/frontdoor/index/index/docId/245 |
Daftar Isi:
- SARI Penelitian dilaksanakan di Sub DAS Ciwidey yang terletak pada koordinat 107° 22 49.23" BT - 107° 33 44.36" BT dan garis lintang 6° 58 34.52" LS - 7° 11 09.54" LS. Secara administratif Sub DAS Ciwidey termasuk ke dalam wilayah Kabupaten Bandung, Propinsi Jawa Barat. Sub DAS Ciwidey termasuk dalam Zona Vulkanik Kuarter berdasarkan pembagian fisiografi (van Bemmelen, 1949). Zona ini didominasi oleh produk gunung api berumur Kuarter. Batuan belum terlitifikasi dengan sempurna, sehingga relatif rentan terhadap proses erosi. Karakteristik morfometri Sub DAS Ciwidey yang diteliti terdiri atas dimensi DAS, bentuk DAS, rasio kebundaran DAS, rasio cabang sungai, kerapatan pengaliran, pola pengaliran, hipsometri interval 25 m, serta stadium erosi pada Sub DAS Ciwidey. Sebagian karakteristik morfometri dianalisis menggunakan pendekatan kuantitatif, sebagian lainnya dengan cara mendeskripsi secara kualitatif. Pola pengaliran yang terdapat di Sub DAS Ciwidey berupa pola pengaliran subdendritik dan subparalel. Dari sepuluh Sub DAS yang diteliti di Sub DAS Ciwidey diperoleh 4 Sub DAS berbentuk paralel, 3 Sub DAS berbentuk bulu burung, 2 Sub DAS berbentuk radials, dan 1 Sub DAS kompleks. Nilai rasio cabang sungai (Rb) yang diperoleh dari 10 Sub DAS yang diteliti di Sub DAS Ciwidey berkisar pada rentang 3 sampai 5. Kondisi ini mencerminkan bahwa Sub DAS Ciwidey cenderung berkembang normal dan tidak dipengaruhi tektonik. Berdasarkan analisis kerapatan sungai (Dd) yang dilakukan pada 436 Sub DAS di Sub DAS Ciwidey, diperoleh nilai Dd yang dominan pada kategori sedang dengan kisaran 0,25 - 10. Nilai Dd ini menunjukkan bahwa alur sungai melewati batuan dengan resistensi keras sehingga material yang terangkut oleh aliran sungai juga sedikit. Analisis variabel hipsometri interval 25 m yang dilakukan pada 12 Sub DAS, dapat diambil kesimpulan bahwa seluruh Sub DAS tersebut berada pada stadium erosi muda hingga menengah dengan kategori nilai yang berkisar 0,55 ≥ HI > 0,45. Hasil analisis hipsometri lereng terhadap variasi litologi di Sub DAS Ciwidey dapat disimpulkan bahwa litologi Tmbe dan Ql memiliki stadium erosi lebih lanjut dibandingkan litologi Qv yang berumur lebih muda. Hal ini dapat dihubungkan dengan nilai kerapatan pengaliran sub DAS pada litologi Tmbe dan Ql yang lebih tua memiliki nilai kerapatan pengaliran yang lebih tinggi dibandingkan pada litologi Qv yang lebih muda, sehingga dapat dijelaskan batuan hasil gunung api tua memiliki sifat resistensi yang lebih lunak atau bersifat lebih permeabel dibandingkan batuan hasil gunung api muda. Kata kunci : hipsometri, morfometri, Sub DAS, Ciwidey. ABSTRACT The research area is located in Ciwidey subwatershed. Geographically, Ciwidey subwatershed lies between 107° 22 49.23" - 107° 33 44.36" East Longitude and 6° 58 34.52" - 7° 11 09.54" South Latitude. Administratively, Ciwidey subwatershed area is located at Bandung Regency, West Java Province. Based on regional physiography, Ciwidey subwatershed stated as Quaternary Volcanic. Quaternary volcanic zone is an area which dominated by quarternary young volcanic products. As a result this quarternary volcanic zone relatively susceptible to erosion. Morphometry characteristics of Ciwidey subwatershed consist of broad, length, and width of watershed, watershed form,circularity ratio, bifurcation ratios, drainage density, drainage patern, 25 m interval hipsometric, and also erosional stadium of Cikeruh watershed. Most mormphometric characteristics were analyzed using a quantitative approach, others by way of a qualitative description. Flow pattern of the river contained in this Ciwidey subwatersheds are subdendritic and subparallel pattern. From the ten studied sub-watershed in the Ciwidey watershed gained 4 sub watersheds shaped parallel, 3 shaped feathers , 2 shaped radial, and 1 shaped complex. Bifurcation ratio (Rb) were obtained from 10 sub-watershed from Ciwidey subwatershed. Rb dominant values obtained in the range from 3 to 5. This means that the Ciwidey subwatershed is not affected by tectonic. Based on the analysis of river density (Dd) conducted on 436 sub-watershed in the Ciwidey subwatershed, Dd values obtained were dominant in the middle category with values ranging from 0,25 - 10. Dd values that are categorized as this indicates that the river flow through the rock with hard resistance so that the material is transported in the flow of the river is also a little. Interval 25 m hypsometric analysis were performed on 12 sub-watersheds in the Ciwidey subwatershed, it can be concluded that the entire sub-watershed is located in the young to middle-stage erosion. By category HI values ≥ 0.55> 0.45. Hipsometric variable in response to litologhy variations in Ciwidey subwatershed can be concluded that the older Tmbe and Ql lithology have a further erosion stage than the Qv lithology. It can be connected with the drainage density value where sub – watershed that contains older Tmbe and Ql lithology has drainage density value higher than sub – watershed that contains younger Qv lithology, so it can be explained that the older volcanic products is more resistancely softer or is more permeable than the younger volcanic products. Keywords : hipsometry, morphometry, sub – watershed, Ciwidey.