Evaluation of Bozem and Drainage Channels of Jade Hamlet Residential in Gresik

. Drainage refers to a vital component for water disposal so that a region or area can hinder potential puddle due to excessive water on the land surface. Therefore, a good plan adjusting the land condition of residential area belongs to a fundamental matter. Jade Hamlet Residence is located on Hulaan highway, Hulaan Urban Village, Menganti District, Gresik Regency, covering an area ±20 hectares and consisting of housing area, park, public facility, and catchment area. The drainage channel at this residence serves as the drainage for rain water and household dirty water disposal. During the rainy season in 2018 and 2019, the channel and bozem or drainage basin of this residence encountered overflowing and eventually caused puddle. To overcome this problem, the capacities of bozem and channel are in need of analysis and evaluation so as to figure out the runoff volume that can be accommodated in the bozem and investigate the discharge planned in the drainage channel by employing Log Person III method, chi-square distribution fit test, Kolmogorov-Smirnov test, rational formula, and exponential method. The results of analysis and evaluation demonstrated that the bozem capacity could not afford the runoff discharge (298.35 m3 > 309.55 m3), thereby demanding additional length and depth against the existing bozem. Meanwhile, the calculation of flood discharge planned for the drainage channels of S4.Ry3, S6.Ry1, S6.D1, S6.I2, S6.Cs1, S6.Rc1, S6.Rc2 indicate that they need redesigning by altering the channel dimension as the discharge capacity exceeds the channel.


Introduction
The rapid population growth in Surabaya Indonesia is currently leading to fast development in the surrounding area, one of which is residential areas in the Menganti District. The trade and services development also occurs in the district with population growth. The increasing number of residential buildings in the Menganti District causes changes in land use and reduced water infiltration into the ground. Drainage is an essential component of water disposal to an area protected by excess water on the ground surface caused inundation. Drainage needs planning following the land conditions of a residential area so that water runoff to the drainage channel can be functioned optimally and does not cause an inundation [1]. Routine and periodic maintenance of residential drainage channels also needs to be carried out so that there is no sediment at the bottom of the drainage channel caused by waste from residents. The residence is a collection of houses completed with facilities, infrastructure, and public utilities to attempt the fulfillment of a livable home, both in urban and rural areas. The Jade Hamlet Residence locates on Raya Hulaan Street, Hulaan Village, Menganti District Gresik Regency, covering an area of about 20 hectares, and consists of residential areas, roads, parks, public facilities, and catchment areas. The drainage channel in this residence serves as a channel for rainwater and household dirty water disposal. The increasing development in this residence causes inundation when it rains. Then it is necessary to analyze the dimensions of the channel so it can accommodate rainwater discharge and dirty water discharge.

Design of Channels and Bozem
Water drainage and drainage systems in urban canals include settlements, industrial or commercial areas, schools, hospitals, public facilities, sports fields, parking lots, electrical or telecommunications installations, airports, or other infrastructure. The drainage network pattern includes rectangular, parallel, iron grid, natural, radial, and nets.
Rainfall was obtained from estimates of several rain stations/rainfall observation points. Calculation of the average rain using the average equation = 1 + 2 + 3 +⋯+ (1) Where, P = Average rainfall (mm) N = Number of observation points or rain stations P1, P2, …,Pn = Rainfall for each station (mm) Where, Sd = Deviation standard Xi = Data in sample ̅ = Average value n = Number of years of observation Where, Cs is skewness, Cv is coefficient of variation and Ck is kurtosis.
The analysis of the frequency of rain on hydrological data intends to meet the magnitude of events related to the frequency of occurrence, using distribution parameters including the average value of rain height, standard deviation, slope coefficient, coefficient variation, sharpness coefficient [2]- [4]. These parameters to determine the distribution method used include normal, normal log, gumbel, type III log person. The fit test is a data frequency distribution that uses the probability distribution and the value can be estimated so that the frequency distribution can be described, namely Chi-squared and Smirnov-Kolmogorov [5], [6]. The calculation of the flow coefficient is a comparison of the amount of water flowing due to rain in an area with the amount of rain falling in that area. Factors that affect the flow coefficient in an area include rain conditions, land, drainage area shape, the slope of the watershed, riverbed slope, infiltration power, soil porosity, soil permeability, temperature, wind, evaporation, and land use [1].
Where, C = flow coefficient of flow area Ci = flow coefficient according to the type of surface A = Total area of drainage Ai = area of each land use Rain intensity is the height/depth of rainwater per unit time. The general nature of rain is that the shorter the rainfall, the higher the return period and the greater the intensity [1], [4], [7], [8]. If only the daily rainfall is known in the rain data, then the Mononobe equation can be used: Where,  Rainwater discharge is the largest discharge that flows in the drainage channel caused by the rain that falls [9], [10]. Rainwater discharge can be calculated using a rational formula which is influenced by the coefficient of drainage in a planning area, the intensity of rain and the area of the drainage area.
The design flood discharge is the largest discharge occured in the specified planned return period. The amount of the planned flood discharge depends on the calculation of the amount of rainwater and the amount of household water flowing through the drainage channel in the planning area. QR = Qah + Qak

Methodology
The flowchart methodology of this research is available in the Figure 3.

Statistical Parameter Calculation Results
Based on the results of the initial calculation of statistical parameters, the appropriate distribution method is Log Person Type III because it has a condition that the values of Cs and Ck are free, so the distribution is chosen. The calculation will be accepted if the theoretical Chi Square value > the calculated Chi Square value. From the calculation above, the value is 5.991 > 2, so the calculation is accepted. 1  2010  2010  99  86,7  12,30  151,29  1860,87  2  2011  2011  83  86,7  -3,70  13,69  -50,65  3  2012  2012  91  The value of Dmax = 0.0647 with a degree of confidence = 5% and the number of data = 10, then the value of Do = 0.41 is obtained. Because the value of Dmax < Do (0.0647 < 0.41), the equation can be accepted. So based on the calculations, the existing bozem capacity < bozem storage volume (298.35 m3 < 309.55 m3), so that it overflows in the bozem. Thus, bozem needs to be redesigned to be able to accommodate the volume of the bozem reservoir.

Conclusions
According to the calculations above, there are 3 conclusions which presented below: