In Semarang urban coastal areas experience daily flooding from the sea during high tide (tidal flooding). Flourishing residential areas have changed into unhealthy slums with the nuisance of daily flooding in parts of the city. To overcome these problems a polder system was implemented to address the tidal flooding. The Semarang polder system is the first fully operational polder system in a densely populated urban area in Indonesia. This article describes the polder system that prevents flooding in the Eastern part of the city; the Banger polder area. An important element of the polder system is an emergency response plan that prepares for a flood emergency condition. The emergency response plan provides different emergency scenarios and identifies emergency levels and criteria. The management of emergency situations can be divided into four phases, namely mitigation, preparedness, response and recovery. The research results provide a detailed description of four emergency scenarios with 3 emergency levels for each scenario in the Banger polder area. The scenarios are; pumping stations operational damage, high-intensity rainfall in combination with high tide, failure of levees and dams, and an inflow of water from the west and east side of Polder system area.
Global warming resulting in climate change has become a new disaster in the world. One of the changes in climate is the rise of sea water to land surface, which causes tidal flooding. One area that experienced tidal flooding was Kawunganten District, Cilacap, Central Java Province. The area is traversed by the Parit River with the river estuary located in Ujungmanik Village. The problem of tidal flooding in Kawunganten District can be overcome by constructing a moveable weir in the estuary of the Parit River. In planning on the moveable weir, a hydrological analysis is needed to determine the flood discharge plan. Rainfall data used as a basis for calculation of flood discharge at the study site is rainfall data from 3 observation stations namely Cilacap Station, Majenang Station and Ujungbarang Station with the recording period from 2009 to 2018. Calculation of rainfall plan is done using the Pearson Log Method III with a value of T100 = 165.463 mm. The results of the calculation of the flood discharge plan with the haspers method Q100 = 280.989 m3/sec, while the weduwen method Q100 = 132.804 m3/sec and the HSS Nakayasu method Q100 = 102.444. Furthermore, an analysis of tides on the coast of Cilacap Regency with the results of MWL (Mean Water Level) = 110 cm, LWL (Low Water Level) = 20 cm, HWL (High Water Level) = 220 cm.
Dari data nilai lahan yang bersumber dari Badan Pusat Statistik Kabupaten Jepara bahwa di Kelurahan Panggang, Kecamatan Jepara pengalihan fungsi lahan untuk bangunan sangat tinggi yaitu menunjukkan persentase sebesar 70,98 %, Oleh karena itu mengakibatkan area terbuka pada Kabupaten Jepara untuk resapan air hujan khususnya di ruas jalur utama menjadi berkurang sehingga mengakibatkan banjir dan genangan air di lokasi pusat kota. Banjir yang terjadi tingginya mencapai 40 cm sampai 80 cm saat hujan turun area pusat perkotaan terdapat beberapa titik genangan di alun – alun Jepara, jalan kartini, dan kawasan pecinan jepara, dan beberapa ruas jalan lainnya. Pada saluran yang ada di Kelurahan Panggang merupakan salah satu prasarana yang mendukung berfungsinya suatu sistem perkotaan di Kota Jepara. Pada saluran yang ada disepanjang daerah Kali Wiso tersebut sering terjadi genangan setiap musim hujan maka perlu dilakukan kajian untuk menganalisis kapasitas saluran drainase tersebut. Data yang digunakan dalam perencanaan adalah data sekunder. Data sekunder diperoleh dari gambar skema saluran drainase dan data mengenai dimensi saluran serta data hidrologi. Data hidrologi dan hidraulika yang diperoleh kemudian dianalisis untuk memperoleh debit rencana dan kapasitas saluran drainase. Debit rencana dihitung dengan menggunakan metode rasional dan kapasitas saluran dihitung dengan permodelan software HEC RAS 4.1.0 dan EPA SWMM 5.1. Penelitian ini mengkaji tentang Analisa Kapasitas Saluran Drainase untuk mengevaluasi banjir berdasarkan kondisi eksisting saluran drainase yang mempengaruhi terjadinya banjir dengan menggunakan permodelan software HEC RAS 4.1.0 dan EPA SWMM 5.1. Software HEC RAS 4.1.0 . Berdasarkan hasil analisa hidrologi bahwa distribusi yang dipilih adalah Distribusi Gumbel Tipe I dan Distribusi Log Pearson Tipe III. Pada uji kecocokan disimpulkan bahwa metode distribusi Log Pearson Tipe III memenuhi persyaratan karena nilai Dmax -0.0202 kurang dari Do 0.41. dan analisa hidrualika diperoleh dengan software HEC RAS 4.1.0 dan EPA SWMM 5.1. pada kala ulang 1 tahun terdapat 2 titik yang mengalami banjir dan 4 titik yang mampu menampung debit banjir . Titik – titik banjir tersebar dibeberapa daerah di Kelurahan Panggang , yaitu Jl. RA. Kartini dan Jl. Pemuda. Dalam mengatasi banjir diperlukan perencanaan ulang drainase kala ulang 10 tahun guna menciptakan keamanan dan kenyamanan bagi warga sekitar.
The high demand for land to be built on, makes the price of land more expensive. Various efforts were made to get land to build houses on, one of them was by way of coastal reclamation. The pond area initially functioned as a water catchment area, but later became new land through the reclamation process. This will have adverse impacts on the environment such as flooding due to lack of water storage. To overcome the problem of building in the coastal area without reclaiming, is using floating house. A floating house is a building structure that floats on the water surface by leaning to drowned area weight as the weight parameter which the structure could handle. This research is done to analyze the material platform. PVC pipe is used with floating force (Fa) parameter and cost plan analysis. The structure weight analysis total result is 555,887.5 Newton. The floating force of structure platform is 648.792 Newton. The connection system is a bolt connection system that us 3 cm in diameter with an anchor of length 22 cm, and a total of 4 bolts on each connection. Cost plan analysis using PVC pipe costs IDR 379.500.000,00.
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