New approaches to stormwater management in cities Kayseri province Yakut district example

In our country there are 240 rain-gauging stations equipped with pluviographs operated by the General Directorate of Turkish State Meteorological Service (MGM), the gauging beginnings of some of these extending to 1930's. The rainfall data are regularly published by MGM at every other five years and the latest publication date is 2020. In this study, first, using the valid data beyond the missing and the incompatible parts, comprehensive frequency analyses have been performed on 14 standard-duration extreme rainfalls series from 5 minutes to 24 hours of 63 elements each gauged over the period of 1950 − 2020 by a computer package program which was developed in 2010 as the product of a research project supported by Tübitak, and up-to-date intensity-duration-frequency relationships have been obtained for Kayseri. Making use of the relevant technical knowledge practiced by the General Directorate of Water and Drainage Works of Kayseri (KASKİ) also, in this study, a project has been developed for drainage of rainstorm water from Yakut Quarter of Kocasinan District of the town of Kayseri in conjunction with rain harvest and artificial recharge of groundwater, and this project has been compared with the conventional system of stormwater drainage. Impervious ground surfaces keep increasing in municipal areas along with increasing urbanization and population density. Hence, infiltration to the ground decreases, the flowrate of overland flow caused by stormwater increases and flood events take place. An infrastructure providing for an increase in the infiltration rate and storing some of the surface flow is needed to prevent or to alleviate urban flooding. Especially, partitioning of a combined sewerage system carrying both municipal wastewater effluents and rainstorm discharges together into separate systems each conveying these discharges separately will be an effective practice to reduce urban floods. Such sustainable applications as enlarging pervious surfaces, forming rain gardens, and modern cistern applications are needed in recent times, which will bring about a two-fold benefit by reducing flood damages and by supplementing water to groundwater reservoir at the same time. In this thesis study, with the purposes of preventing flooding and at the same time artificially recharging the groundwater reservoir by stormwater in Yakut Quarter of Kocasinan District of the town of Kayseri, based on a design storm of 15 minute duration having a 5 year average return period, both a conventional stormwater drainage system and a modern system of discharging some of stormwater to the available green areas (rain harvest) are designed with the help of the computer package Mskanal which uses the Rational Method. For the conventional system, a network of pipes, the smallest one being a corrugated pipe of 300 mm diameter, and the largest one being the sealed concrete pipe of 2200 mm diameter, is designed which discharges the overall accumulated flowrate to Sarımsaklı Creek to the north of the study area. The total length of the pipes in this system and the approximate total cost are computed to be 22,693 m and 60,524,588 Turkish Lira. For the proposed new system of discharging some of the stormwater to the green areas, the total length of the pipes turn out to be 13,133 m, comprising all corrugated pipes having diameters ranging from 300 mm to 500 mm, and the total cost of this alternative system is computed to be 6,724,956 Turkish Lira. In conclusion, the new system which diverts some of the overland flow resulting from the design storm is proposed as a viable alternative because it is financially more profitable and at the same time it will bring about an intangible benefit of artificial recharge of the groundwater reservoir in the vicinity of the study area. Keywords: Stormwater, Rational Method, Conventional Stormwater System, Rain Water Harvest, Discharge To Green Area