KAJIAN HIDROGEOMORFOLOGI BANJIR DI KOTA GORONTALO
Arqam Laya, Prof. Dr. H. Sudarmadji, M.Eng.Sc.
2013 | Disertasi | S3 GeografiPenelitian ini berfokus pada kajian hidrogeomorfologi dalam memetakan tingkat kerentanan banjir di Kota Gorontalo berdasarkan aspek hidrologi dan aspek geomorfologi. Tujuan penelitian untuk (1) mengkaji karakteristik potensi bahaya banjir menurut satuan pemetaan hidrogeomorfologi Kota Gorontalo, (2) mengkaji tingkat kerentanan banjir satuan pemetaan hidrogeomorfologi dan hubungan tingkat kerentanan dengan variabel hidrogeomorfologi, (3) menentukan zonasi hidro geomorfologi banjir Kota Gorontalo berdasarkan karakteristik penyebab banjir, (4) menyusun solusi dan arahan pengendalian banjir Kota Gorontalo. Lokasi Penelitian Kota Gorontalo. Metodenya menggunakan pendekatan grid, yaitu membagi dataran Kota Gorontalo atas 46 grid. Pengambilan sampel data pada setiap grid berdasarkan metode sistematis, hasilnya di tabulasi/matriks. Analisis data menggunakan metode analisis regresi dan analisis tabulasi silang, selanjutnya dideskripsikan. Hasil penelitian menunjukkan bahwa: (1) analisis varian menunjukkan bahwa secara keseluruhan antara potensi bahaya banjir dan variabel hidrogeomorfologi mempunyai pengaruh yang sangat signifikan. Hal ini ditunjukkan oleh nilai signifikan sebesar 0% kurang dari 1%. Nilai ekspektasinya laju infiltrasi 66,7%, curah hujan 66,7%, saluran drainase 33,3%, bentuklahan 75% dan kemiringan lereng 66,7%. Jenis tanah kurang berpengaruh; (2) analisis hubungan tingkat kerentanan dengan variabel hidrogeomorfologi sangat signifikan. Kawasan terdampak banjir seluas 965,828 Ha (14,47%), terevaluasi laju infiltrasi I4 dan I5 seluas 1744,33 Ha. Curah hujan penyebab banjir ada 4 jenis (a) curah hujan lokal, (b) akumulasi hujan lokal, (c) hujan di hulu DAS LBB (d) akumulasi hujan di hulu DAS LBB. Kondisi saluran drainase kualifikasi buruk (2097,64 Ha), Bentuklahan F (3549,37 Ha) dan bentuklahan D (3121 Ha). Kemiringan Lereng < 7% (3507,84 Ha). Jenis tanah aluvial (3492,31 Ha); (3) Pemetaan zonasi hidrogeomorfologi banjir terdiri atas lima kelas tingkat kerentanan yaitu: kerentanan SR (273,28 Ha), kerentanan R (1.023,339 Ha), kerentanan CR (2302,13 Ha), kerentanan KR (168,77 Ha), kerentanan TR (2.781,95 Ha). (4) Solusi dan arahan pengendalian yaitu saluran drainase berbasis polder, terbagi dalam 3 (tiga) zonasi, yaitu; mintakat barat seluas 1069,83 Ha; mintakat tengah seluas 827,86 Ha; mintakat timur seluas 1369,04 Ha. Berdasarkan hasil penelitian disarankan perlu kajian penelitian lanjutan tentang curah hujan dibagian hulu DAS LBB dan akibat adanya patahan dibagian selatan dikhawatirkan terjadi penenggelaman. Tinggi genangan terevaluasi akibat penggunaan lahan kurang sesuai untuk peruntukkan dan kondisi drainase yang buruk, maka dibutuhkan regulasi tentang penataan ruang berdasarkan zonasi potensi bahaya dan tingkat kerentanan.
This study focuses on the study of hydrogeomorphology in mapping vulnerability of flooding in Gorontalo City. flooded based on aspect of hydrology and the aspect geomorphology in order to (1) examine the characteristics of potential flood hazards by hydrogeomorphological mapping unit of Gorontalo City. (2) assess the vulnerability of flood hydrogeomorphological mapping units and the relationship with the level of vulnerability of hydrogeomorphological. (3) determine the hydrogeomorphological zonation Gorontalo city flooded by the characteristics of the causes of flooding, (4) formulate solutions and Gorontalo City flood control directives. The method used is grid approach, it was to divide the land in Gorontalo City to be 46 grids. Sampling data taking in every grid based on systimatic sampling method, the results can be shown in tabulation/matrix. Data analysis using was to use cross tabulation method, and then it was described. The results of this study shows that: (1) analysis of variance showed that overall the potential flood hazard and hydrogeomorphology variables have a significant influenced. This is demonstrated by the significant value of 0% is less than 1%. Expectation value of the infiltration rate 66.7%, the rainfall rate 66,7%, the drainage 33.3%, the landform 75% and the slope of 66.7%. Soil type not effective, (2) the analysis of the level of vulnerability to hydrogeomorphological variables are very significant. Flood affected area covering 965.828 ha (14.47%), evaluated the rate of infiltration I4 and I5 covering 1744.33 ha. Rainfall causes flooding there are 4 types. Poor drainage conditions (2097.64 Ha). F landforms is 3549.37Ha and D landform area of 3121 Ha. The slope < 7% is 3507.84 Ha (52.6%). Aluvial soil type an area of 3492.31 Ha, (3) mapping of zone of flood hydrogeomorphology in Gorontalo city got five classes of vulnerabilities are: Highly vulnerable (SR = 273.28 Ha), vulnerability (R = 1023.339 Ha), vulnerable enough (CR = 2302,13 Ha), less vulnerable (KR = 168.77 Ha), not vulnerable (TR = 2781.95 Ha). (4) Based on the guidance development polder drainage channels are divided into 3 (three) zoning, namely western zone (1069.826 Ha); zone center (827,858 Ha); and zone east (1369.04 Ha). Based on a needs assessment study recommended further research on rainfall upstream catchment area LBB and due to the fault occurs in the south feared drowning. Evaluated water level due to lack of appropriate land use for the designation and poor drainage conditions, then the required regulation on spatial planning based on zoning potential hazards and vulnerability.
Kata Kunci : banjir, Gorontalo, hidrogeomorfologi, zonasi kerentanan
