No abstract

Inundation of flood and rob (flood due to high tides) in Semarang City is increase wtithin area and depth. It be more seroius condition because of land subsisdence that happened in coastal area of Semarang City. This research is foccused on prediction and mapping of inundation flood and rob due to land subsidence effect in East Semarang, especially Tenggang Watershed and Sringin Watershed. On this research, data analysis including analysis of land subsidence, analysis of hydrological data, analysis of flood discharge with HEC-HMS, hydraulics analysis with HEC-RAS and then mapping the results of the flood inundation with Arc GIS. The inundation will be create with overlay the DEM of flood water level and DEM of topographic. According to the results of analysis is known that minimum land subsidence is 0 cm/year that happened in south area of Semarang and more higher ini north area with maximum land subsidence is 5.58 cm/year. On periode   2014-2031, the contribute of land subsidence to increase the inundation of flood and rob is 1.39%/year.

Rawa Pening is a natural lake as a source of water for Tuntang River which is used for hydropower, raw water source, main irrigation water source in Glapan weir located in Grobogan District, Central Java provinces. Rawa Pening will be developed as location of national and international ecotourism. An Optimal Water Resources Management is required with several studies. This study is the beginning of a series of studies planned to determine the potential of embungs and its utilization as flood control, sediment control of Rawa Pening and for reducing weeds growth.

Abstrak:Dalam suatu WS/DAS, pos pencatatan curah hujan biasanya lebih banyak ditemui dibandingkan dengan pos pencatatan debit. Banyaknya jumlah pos hujan menimbulkan permasalahan dalam biaya operasi dan pemeliharaan. Penelitian ini bertujuan untuk menentukan pos hujan yang paling berpengaruh pada DAS Bd. Katulampa. Analisis dilakukan dengan metode Stepwise yang merupakan analisis multi correlation, dalam hal ini data hujan bulanan sebagai variabel bebas dan data debit bulanan sebagai variabel tidak bebas. DAS Bd. Katulampa dipengaruhi oleh 13 pos hujan. Akan tetapi karena keterbatasan data, analisis dilakukan pada 5 Pos Hujan yaitu Pos Perkeb. Gn. Mas, Pos Gunung Mas, Pos Panjang, Pos Pasir Muncang dan Pos Katulampa. Hasil analisa dengan multi correlation menunjukkan bahwa pertambahan nilai korelasi bertambah dari kombinasi 2,3 dan 4 pos hujan. Akan tetapi pada kombinasi 5 pos hujan, pertambahan nilai korelasi tidak lagi signifikan. Hal ini bisa disimpulkan bahwa pada DAS Bd. Katulampa, pencatatan pos hujan cukup terwakili dengan kombinasi 4 pos hujan antara lain Pos Perkeb. Gn. Mas, Pos Panjang, Pos Pasir Muncang dan Pos Katulampa. Kombinasi 4 pos hujan ini kemudian di cek dengan standar WMO. Polygon thiessen yang dihasilkan 4 pos hujan hasil analisis, menghasilkan luas pengaruh pos hujan maksimum adalah 50.57 km2 yaitu Pos Pasir Muncang dan minimum 15.46 km2 Pos Katulampa. Artinya dengan 4 pos hujan tersebut, luas pengaruh pos hujan masih masuk dalam ketentuan yang disyaratkan oleh WMO.Kata-kata kunci: pos hujan, pos debit, multi correlation, stepwiseAbstract:In a WS / DAS, the rainfall recording post is usually more common than the debit recording post. The large number of rain stations has caused problems in operating and maintenance costs. This study aims to determine the most influential rainfall items in the watershed Bd. Katulampa. The analysis was carried out using the Stepwise method which is a multi correlation analysis, in this case monthly rainfall data as the independent variable and monthly discharge data as the dependent variable. DAS Bd. Katulampa is affected by 13 rain posts. However, due to data limitations, the analysis was carried out on 5 Rain Posts, namely Perk Perkeb. Mt. Mas, Gunung Mas Post, Pos Panjang, Muncang Sand Post and Katulampa Post. The results of the analysis with multi correlation show that the correlation value increases from the combination of 2.3 and 4 rain posts. However, in the combination of 5 rain posts, the correlation value is no longer significant. It can be concluded that in the watershed Bd. Katulampa, the recording of rain posts is adequately represented by a combination of 4 rain posts, including the Pos Perkeb. Mt. Mas, Long Post, Muncang Sand Post and Katulampa Post. The combination of the 4 rain posts is then checked with the WMO standard. Polygon Thiessen produced by 4 analysis results, the maximum area of influence is 50.57 km2, that is Pasir Muncang Post and minimum 15.46 km2 Katulampa Post. This means that with the 4 rain posts, the broad influence of the rain post is still included in the conditions required by the WMO.Keywords: rain post, debit post, multi correlation, stepwise.