sadevesiviemäreinä

Sadevesiviemäreinä, meaning "rainwater sewers" in Finnish, refers to the network of underground pipes designed to collect and transport rainwater and surface runoff away from urban areas. These systems are crucial for managing stormwater, preventing flooding, and protecting infrastructure. The primary purpose of rainwater sewers is to channel water from streets, rooftops, and other impervious surfaces into a designated discharge point, which can be a river, lake, ocean, or a specialized treatment facility.

The design and capacity of rainwater sewer systems are carefully calculated based on factors such as expected rainfall intensity, the size of the drainage area, and the permeability of the ground. In many cities, rainwater sewers are separate from sanitary sewers, meaning they carry only stormwater and do not mix with wastewater from homes and businesses. This separation is important because it reduces the volume of water that needs to be treated at wastewater treatment plants, especially during heavy rain events.

However, in some older urban areas, combined sewer systems exist, where both rainwater and sanitary sewage flow through the same pipes. During heavy rainfall, these combined systems can become overloaded, leading to combined sewer overflows (CSOs), where untreated sewage and stormwater are discharged directly into waterways. Modern urban planning increasingly emphasizes the importance of separate sewer systems and the implementation of sustainable urban drainage systems (SUDS) to mitigate these issues. SUDS include features like permeable pavements, green roofs, and retention ponds, which help to reduce the amount of runoff entering the sewer system and promote natural water infiltration.