The purpose of this study is to find the value of the discharge coefficient (Cd) on a sieve with a circular perforated plate so that it can be used for application in the field. The method used is to make a physical model test of the screen weir in the laboratory with a width of 40 cm and a length of 797 cm, then the screen is made variations in the diameter of the hole 6, 8, 10 and 12 mm, flowrate Q = 453–4 481 cm3∙s–1 and the slope of the screen θ = 20–45°. The result was quite ef-fective, the sediment did not enter above the screen and did not clog the screen even the catch was quite good about 80% of the screen rods. The discharge coefficient (Cd) is directly proportional to the square value of the number Froude (Fr), the slope of the screen (θ) and the ratio of distance, diameter of the screen (a:d) and inversely proportional to the value of the specific energy square (E). From modelling the average value of the discharge coefficient (Cd) between 0.1–2.75 with NSE = 0.71, MAE = 0 and RMSE = 0.12.
Flood inundation processes in urban areas are primarily affected by artificial factors such as drainage facilities, local al-terations of topography and land uses. The objective of this study is to examine the capability of hydrological model SI-MODAS to estimate runoff and investigating the utilization of storage well in controlling runoff in a residential area. The result of the estimated runoff from the hydrological model was compared with the existing capacity of the drainage channel to identify which channel experienced the problem of inundation. The location of inundation was used to determine the location and number of storage well. The results showed that SIMODAS model could be applied in runoff analyses with 8.09% of relative error compared with runoff depth from field measurement. The existing capacity of the channel could not accommodate runoff Q10yr where the inundation discharge was approximately 0.24 m3·s–1 (at outlet point 1) and 0.12 m3·s–1 (at outlet point 2). The inundation problem was overcome by using a combination system between channel normalization (reduce 35% of total inundation discharge) and storage well system (reduce 65% of total inundation discharge). The storage well was designed at 20 locations (at outlet point 1) and 16 locations (at outlet point 2) which each well had a discharge of 0.0058 m3·s–1. The storage well combined with channel normalization could be used as an alternative way to solve inunda-tion problems in a residential area considering the constraint of land space limitation in the urban area.
Reservoirs have a very important function in providing multi-sector water requirements. In the future, reservoirs not only serve to store and available water can also be used as disaster mitigation instruments. The completeness of hydrological measurements in reservoirs can be expanded more widely for climate change mitigation. The reliability of the reservoir capacity varies greatly depending on the El-Nino character that occurs among them El-Nino is weak, moderate, strong and very strong. The El-Nino characteristic is very influential on the period of water availability, the increase of evaporation capacity and decrease of reservoir capacity. Analysis of the reliability of the reservoir volume due to El-Nino using the Weibull equation. The deficit reservoir was calculated using the concept of water balance in the reservoir that is the relationship between inflow, outflow, and change of storage at the same time. Based on the results of the analysis showed that the evaporation increase and the decrease of reservoir capacity had a different pattern that is when the evaporation capacity started to increase at the same time the reservoir capacity decreased significantly. The correlation coefficient between evaporation capacity increase and decrease of reservoir water capacity are consecutively –0.828, –0.636, and –0.777 for El- Nino weak, moderate and very strong respectively. At the reservoir capacity reliability of 50% reservoir has a significant deficit. When weak El-Nino the deficit is 2.30∙106 m3, moderate: 6.58∙106 m3, and very strong 8.85∙106 m3.