KAJIAN EROSI TANAH PERMUKAAN DENGAN METODE USLE DAN METODE PEMETAAN CEPAT (RAPID MAPPING) DI SUB DAS CIMANUK HULU PROVINSI JAWA BARAT

RAHMAT RAZALI, Dr. Danang Sri Hadmoko, M.Sc.

2013 | Tesis | S2 Geografi

Penelitian ini bertujuan untuk : (1) Menganalisis bahaya erosi tanah permukaan dengan Metode USLE dan Metode Pemetaan Cepat (Rapid Mapping), (2) Menguji akurasi spasial bahaya erosi tanah permukaan Metode Pemetaan Cepat (Rapid Mapping) terhadap Metode USLE dengan menggunakan skala piksel, (3) Menentukan arahan teknik konservasi tanah berdasarkan kriteria bahaya erosi tanah permukaan. Penentuan pendugaan erosi Metode USLE dilakukan dengan pendekatan satuan analisis lahan berdasarkan tumpangsusun bentuklahan, erosivitas (R), erodibilitas (K), panjang dan kemiringan lereng (LS), penggunaan dan pengelolaan lahan (CP) kemudian di klasifikasikan dalam bahaya erosi. Metode Pemetaan Cepat dilakukan 3 jenis pemodelan berdasarkan bobot dan indeks sensivitas dari variabel penutupan lahan, kemiringan lereng dan persentase tanah terbuka untuk mendeliniasi bahaya erosi. Penelitian ini menggunakan dengan skala piksel guna menguji akurasi Metode Pemetaan Cepat terhadap bahaya erosi USLE melalui analisis matrik kesalahan (matrix confusi) dan kappa (K). Penelitian Metode USLE menunjukkan bahwa luas bahaya erosi Sangat Berat 26,69 Km2 (17,07%), Berat 22,84 Km2 (14,61%), Sedang 19,84 Km2 (12,69%), Ringan 54,88 Km2 (35,10%) dan Sangat Ringan 32,10 Km2 (20,53%). Sedangkan Metode Pemetaan Cepat untuk Model 1 menghasilkan bahaya erosi Berat 0,08 Km2 (0,07%), Sedang 11,12 Km2 (9,38%), Ringan 84,98 Km2 (71,68%) dan Sangat Ringan 22,36 Km2 (18,87%). Model 2 menghasilkan bahaya erosi Berat 0,5 Km2 (0,42%), Sedang 11,58 Km2 (9,77%), Ringan 84,11 Km2 (70,95%) dan Sangat Ringan 22,36 Km2 (18,86%). Model 3 menghasilkan bahaya erosi Sangat Berat 0,01 Km2 (0,01%), Berat 0,2 Km2 (0,17%), Sedang 4,42 Km2 (3,73%), Ringan 43,88 Km2 (37,01%) dan Sangat Ringan 70,04 Km2 (59,08%). Akurasi bahaya erosi yang dihasilkan keseluruhan model Pemetaan Cepat dalam katagori sedang, namun Model 3 menghasilkan nilai akurasi. Nilai masingmasing overall accuracy dan kappa yang dihasilkan adalah Model 1 : (74,69 %; K (0,54), Model 2 : (74,19%; K 0,53) dan Model 3 : (73,93%; K 0.57). Arahan teknik konservasi tanah pada spasial bahaya erosi di kawasan lindung dan penyangga masing-masing seluas 174,02 Ha dan 139,15 Ha diarahkan untuk Hutan Kemasyarakatan, untuk kawasan tanaman tahunan seluas 137,07 Ha diarahkan untuk Hutan Rakyat, sedangkan pada kawasan budidaya tanaman semusim diarahkan pengelolaan dengan tanaman jalur (strip cropping)/tumpangsari seluas 12,49 Ha.

This study aims to: (1) analyze erosion hazard by using USLE and Rapid Mapping Methods, (2) test spatial accuracy of Rapid Mapping erosion hazard method to USLE method by using pixel scale, (3) determine soil conservation technique directive based on criteria of erosion hazard and area function. Determination of USLE method erosion prediction was conducted with analysis of land unit approach based on landform analysis overlay, erosivity (R), erodibility (K), length and slope (LS), land use and management (CP), which are then classified into the USLE erosion hazard. In the Rapid Mapping method, three kinds of modeling based on weight and sensitivity index of the land cover, slope and the percentage of bare soil variables were made to delineate erosion hazard. This study uses the pixel scale to test the accuracy of the Rapid Mapping Method for USLE erosion through the analysis of the confusion matrix and Kappa (K). The results of USLE method show that the area of very severe erosion hazard is 26.69 Km2 (17.07%), area of severe erosion hazard is 22.84 Km2 (14.61%), area of medium erosion hazard is 19.84 Km2 (12.69%), area of light erosion hazard is 54 ,88 Km2 (35.10%), and area of very light erosion hazard is 32.10 Km2 (20.53%). Result of Rapid Mapping Method show for Model 1 produces very light erosion hazard in area of 22.36 Km2 (18.87%), light erosion hazard in area of 84.98 Km2 (71.68%), medium erosion hazard in area of 11.12 Km2 (9.38%), and high erosion hazard in area of 0.08 Km2 (0.07%). On Model 2 produces erosion hazard in area of 22.36 Km2 (18.86%), light erosion hazard in area of 84.11 Km2 (70.95%), medium erosion hazard in area of 11.58 Km2 (9.77%), and high erosion hazard in area of 0.5 Km2 (0,42%). Model 3 produces very light erosion hazard in area of 70.04 Km2 (59.08%), light erosion hazard in area of 43.88 Km2 (37.01%), medium erosion hazard in area of 4.42 Km2 (3.73%), high erosion hazard in area of 0.2 Km2 (0.17%) and very high erosion hazard in area of 0.01 Km2 (0.01%). The result of confusion matrix demonstrates that the accuracy of all models Rapid Mapping is in medium category, and model 3 yields a better accuracy value than the others. Values of each generated overall accuracy and kappa are Model 1: 74.69%; K (0.54), Model 2: 74.19%; K (0.53) and Model 3: 73.93%; K (0.57). Proposing ideas of the soil conservation technique in protected areas and buffer area of 174.02 and 139.15 Ha directed to community forest, while 137.07 ha of annual crops geared proposed for private forest, while the seasonal crop area (12.49 Ha ) directed of the plant strip cropping / cropping area.

Kata Kunci : USLE, Pemetaan Cepat, bahaya erosi, matrik kesalahan dan kappa, arahan teknik konservasi tanah