Investigation stormwater inlets in urban areas : Example of ITU Ayazaga campus

In this study, information was given about inlets which are generally used in urbans and chosen by people to live in developed countries like United States in order to remove surplus water after rain. In developed countries, public living areas are designed in a way that negative effects on the life of community are either prevented or reduced. In order to inhibit the disturbing results of rainfall water on human life, stormwater drainage systems are installed at urban areas which is one of the mentioned public living areas. Inlets are parts of the stormwater drainage systems. Stormwater drainage is important for preventing damage to highways, traffic, erosion and landslide. Effective drainage on the roads are important for road maintenance, conservation and traffic safety. Water on the road can cause traffic blockage, reduction in skid resistance, reduction in movement capability on wet floor, reduction in eyesight because of splash and harmful effects on driving ability. By telling the importance of rainwater drainage in urbans, features that is needed economically, structurally and hydraulically, physical features, advantages and disadvantages, features provided for pedestrians and vehicles, their location information on gutters and produdictiveness of the four main types of inlets, namely curb-opening inlets, grate inlets, combination inlets and slotted inlets are mentioned. Stormwater drainage on the road requires importance surface drainage, gutter runoff and inlet capacity. Design of these elements is dependent to rain frequency and permitted diffusion of rain water on the pavement. Minimum design frequencies and diffusion proportion according to highway type and traffic flow speed are suggested by FHWA (Federal Highway Administration). There are criteria need to be considered when planning the rainwater inlet. These criteria are curbs close to the traffic, curbs that have distance to the traffic, and slope of the streets. Information is given due to these criteria. In addition, placed of the inlets on the streets and crossroads are examined by economically, suitability, and importance. Also, vehicle, pedestrian, bicycle safety and clogging of inlets are being considered while planning the project. Flow rate of rainfall on the highway pavement, Information about the Rational Method which is a rainfall estimation method based on density is presented. When minimum design frequencies are compared between FHWA and Turkish Federal Highway Administration; It is observed that FHWA has a more detailed table. Gutter capacities are formulated by Manning Formula by using four types of gutters commonly used on street which are uniform section gutter, composite section gutter, circular gutter, and V-shape gutter. Information has been provided on the capacity of discharges accordance with continuous slope and sag locations of four main types of inlets, namely curb-opening inlets, grate inlets, combination inlets, and slotted inlets. Experimental data of the Federal Highway Administration on tip ızgaraları are showed for grate inlet on street gutter. Inlets are subject of clogging. Clogging factor depends on state of the debris and trush on the street. During the rainfall, inlets are usually loaded with debris by the first-flush runoff volume. As a popular application of street drainage; 50% clogging for the single grate inlet and %10 clogging for the inlets on the curb openning are considered for design. Current placement of the inlets on inner roads of Ayazağa Campus located at Maslak in Istanbul Technical University are examined by considering spread of the water on the streets and putting inlets in the appropriate places. At the end of the review, things to change and suggestions are presented. Since there is not any research on capacity of grate inlets in Turkey so investigation of capacity calculation is not performed in example of Istanbul Technical University Ayazaga Campus. Also time of concentration calculation performed table from Turkish Federal Highway Administration Design Manual in example of Istanbul Technical University Ayazaga Campus.