Urbanization has a significant impact on the amount of surface runoff. Percolation is reduced due to a high percentage of impervious materials covering the soil, evapotranspiration is decreased due to vegetation clearing, and there is not enough space for naturally formed depressions that would retain water within urban areas. Studies show that both surface runoff amount and velocity in these areas increase up to severalfold. Such runoff contains more pollutants as well.udThe first part of this thesis describes the characteristics of surface runoff, drainage types and the impact of urbanization on runoff. It also contains an overview of measures for urban runoff prevention and mitigation, which include trees, green roofs, rainwater harvesting, stormwater planters, deepened green belts, dry and wet detention basins, constructed wetlands, permeable paved surfaces, infiltration basins as well as other recharge and discharge structures in sewer systems.udThe second part contains a detailed presentation of the rational method, which is often used to calculate peak runoff from smaller drainage areas. It forms the basis of the modified rational method that helps estimate the necessary runoff retention volume by taking into account the allowed discharge. We studied the actual effects of urbanization in three cases, by monitoring the change inudrunoff coefficient, time of concentration and runoff amount. We calculated the necessary urban runoff retention volume that would not affect conditions downstream.
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