PENGARUH HUJAN TERHADAP SEDIMEN PADA OVERLAND FLOW DI PERMUKIMAN DUSUN BANTENG, SINDUHARJO, NGAGLIK, SLEMAN

RIZKA RATNA SAYEKTI, Prof. Dr. Sudarmadji, M.Eng.Sc.

2017 | Skripsi | S1 GEOGRAFI DAN ILMU LINGKUNGAN

Permukiman Dusun Banteng memiliki permasalahan sedimentasi pada saluran drainase, sumur resapan, dan jalan. Sumber sedimen berasal dari erosi tanah, material bangunan, kotoran ternak, material yang terbawa kendaraan, dan abu vulkanik akibat erupsi gunungapi yang terbawa hingga permukiman. Tujuan penelitian ini adalah: 1) menganalisis pengaruh hujan terhadap debit aliran dan pengaruh debit aliran terhadap berat sedimen pada overland flow dalam suspended load; 2) menanalisis karakteristik ukuran butir sedimen pada muatan bed load; dan 3) mengidentifikasi dampak sedimentasi terhadap lingkungan di permukiman Dusun Banteng. Data yang dibutuhkan yaitu kadar sedimen, tinggi muka air, debit aliran, curah hujan, ukuran butir sedimen, dan dampak sedimentasi. Data kadar sedimen, tinggi muka air, dan debit aliran digunakan untuk mencari berat sedimen pada suspended load dalam sekali kejadian hujan. Berat sedimen tersebut dicari hubungannya dengan curah hujan menggunakan analisis korelasi dan regresi. Analisis karakteristik ukuran butir sedimen pada bed load menggunakan kurva kumulatif persentase. Berdasarkan analisis karakteristik suspended load dan bed load beserta observasi, maka dapat dirumuskan dampak-dampak sedimentasi yang terjadi di Dusun Banteng. Hasil penelitian menunjukkan curah hujan memiliki korelasi positif terhadap debit aliran dan debit aliran juga memiliki korelasi positif terhadap berat sedimen pada suspended load di saluran drainase. Karakteristik ukuran butir bed load di dalam sumur resapan bertekstur lebih halus dibandingkan dengan bed load di luar sumur resapan. Jarak aliran overland flow tidak berpengaruh terhadap kekasaran bed load. Kekasaran bed load lebih dipengaruhi oleh sumber sedimen. Sumber sedimen yang berasal dari halaman rumah lebih kasar daripada sedimen yang berasal dari jalan dan atap rumah. Sedimentasi berdampak pada berkurangnya fungsi saluran drainase dan sumur resapan dalam mengalirkan overlandflow. Akibatnya, sering terjadi banjir saat hujan sangat lebat. Dampak sedimentasi menyadarkan masyarakat untuk menjaga lingkungan sekitar dengan membersihkan sedimentasi di saluran drainase dan sumur resapan.

Banteng settlement has sedimentation problems in drainage channel, absorption well, and road. Soil erosion, building materials, livestock manure, vehicle-borne material, and volcanic ash are source of sedimentation. The aim of this research are: 1) to analyze the effect of rain on overland flow and the effect of overland flow on sediment weight in suspended load; 2) analyze the characteristics of grain size of sediment in the bed load; and 3) to identify the impact of sedimentation in Banteng settlement. The data required in this research are concentration of sediment, water level, flow discharge, rainfall, sediment grain size, and sedimentation impact. Consentration of sediments, water levels, and flow discharges were used to calculate sediment weight in suspended load. Through the use of correlation and regression techniques, sediment weight and rainfall relationships were expressed. Analysis of grain size of sediment in bed load using percentage cumulatice curve. Based on the analysis of suspended load and bed load characteristics along with observation, it can be formulated sedimentation impacts that occured on Banteng settlement. The results show that rainfall has a positive correlation to flow discharge and flow discharge has a positive correlation to sediment weight in suspended load in the drainage channel. Grain size of sediment in absorption well has smoother texture than the bed load outside the absorption well. Overland flow distance has no effect on bed roughness. Bed roughness is more influenced by sediment sources. The sediment source from the home page is more rough than the sediments coming from the road and the roof. Sedimentation affects the reduced function of drainage channels and absorption well to drain overland flow. As a result, floods often occur when the rain is very heavy, the effects of sedimentation made people aware of the environment by cleaning up the sedimentation in the drainage and absorption well.

Kata Kunci : sediment, suspended load, bed load, overland flow, rainfall