Metode hidrograf satuan sintetis adalah metoda yang populer digunakan dan memainkan peranan penting dalam banyak perencanaan di bidang sumber daya air khususnya dalam analisis debit banjir DAS yang tidak terukur. Metode ini sederhana, karena hanya membutuhkan data-data karakteristik DAS seperti luas DAS dan panjang sungai dan dalam beberapa kasus dapat juga mencakup karakteristik lahan digunakan. Oleh karena itu, metode ini merupakan alat berguna untuk mensimulasikan aliran dari DAS tidak terukur dan daerah aliran sungai mengalami perubahan penggunaan lahan. Untuk mengembangkan hidrograf satuan sintetis, beberapa metoda telah tersedia. Beberapa metoda hidrograf satuan sinteteis seperti cara Nakayasu, Snyder-Alexeyev, SCS, dan GAMA-1 sangat populer dan umum digunakan di Indonesia untuk menghitung debit puncak dan bentuk hidrograf banjir. Makalah ini menyajikan suatu pendekatan sederhana untuk menentukan hidrograf satuan tak-berdimensi yang konsisten berdasarkan prinsip konservasi massa. Hidrograf satuan dapat dibuat dengan menggunakan satu fungsi tunggal sederhana (HSS ITB-1) atau menggunakan dua fungsi sederhana (HSS ITB-2) yang dikombinasikan dengan faktor debit puncak yang dapat disesuaikan secara otomatis berdasarkan rasio antara luas DAS dan luas hidrograf satuan yang dihitung secara numerik menggunakan prosedur tabulasi sederhana.

Abstrak Daerah tangkapan sungai Komering Hulu memberi kontribusi nyata terhadap daerah aliran sungai 135,88 m3/det (1971-1991 dan 1992-2010 135.88 m3 / sec (1971-1991 and 1992-2010

The characteristic hydrology of a watershed is playing a major role in ensuring water resource availability. Rainfall and runoff responses in catchment area are part of the hydrology cycles. There are several factors to determine the characteristic of hydrology at the watershed, i.e. geological, region, soil and land cover. The existence of water resources is very substantial for surroundings. The rapid development in various sectors leads to water demands increase. Optimum utilization of water resources is needed in the sustainability of water resources or the need for integrated water resources management. The consequence of development is land use change, resulting in changes inflow characteristics, flood during the wet season and drought or discharge decrease in the dry season. Many studies associate higher watershed land cover with lower baseflows, attributed to high evapotranspiration rates, while other studies indicate increased baseflow with higher watershed land cover due to higher infiltration and recharge of subsurface storage. Adaptation and mitigation efforts are required to anticipate changes in the flow characteristics. The factors are key controls on base flow through their influence on infiltration, catchment and subsurface storage properties. This review underscores the need for more research that multiple aspects of the watershed system in explaining base flow. The result of average base flow and total flow ratio during 40 years (1971-2010) is 0.296 and the class of the hydrologic function as a BF / TF ratio value which indicated very poorly hydrology function of upstream Komering, although in certain hydrologic function was still in the good category.

Synthetic unit hydrograph (SUH) methods are popular and play an important role in many water resources analyses of un-ganged watersheds. These methods are simple, requiring only an easy determination of watershed characteristics, such as catchment area and river length. In some cases, they may also include landuse characteristics and serve as useful tools to simulate runoff from watersheds undergoing land-use change. To develop a synthetic unit hydrograph, several synthetic unit hydrograph models such as HEC-HMS, Nakayasu, SnyderAlexeyev, SCS, and GAMA-1 are commonly used in Indonesia. In this paper, a new method for computing the synthetic unit hydrograph based on mass conservation principles is presented. This mass conserving synthetic unit hydrograph calculation procedure, called the ITB SUH calculation method, has been implemented in the development of ITB-1 and ITB-2 SUH. The unit hydrographs are synthesized by using either a simple single function (ITB-1) or using two simple functions (ITB-2) combined with automatic adjustable peak discharge factors. Some applications of the method in computing design floods of small-and medium-size catchment are presented. The results show that, although input requirements for the ITB SUH calculation method are simple and the calculation is easy, the final results agree well with other methods developed previously.

Persamaan mild-slope yang diturunkan Kirby (1986) dapat diterapkan untuk simulasi transformasi gelombang dari perairan dalam menuju pantai. Pada paper ini dikembangkan model Kirby dengan memperhatikan faktor arus. Pengaruh arus pada transformasi gelombang tersebut diselesaikan dengan metode selisih hingga. Berdasarkan verifikasi model numerik dengan analitik menunjukkan bahwa perbedaan kecepatan rata-rata arus longhsore kurang dari 5%, artinya model numerik ini dapat mensimulasikan arus akibat induksi gelombang dengan baik. Verifikasi model gelombang dengan hasil penelitian Johnson (1952), Wiegel (1962) dan Wei (1998) menunjukkan adanya kemiripan, sedangkan perbedaan yang ada karena pada model mempertimbangkan faktor arus.