Urban Rivers

General Goals:

• faster flow

• free up land for agriculture

• transpport

• combination with dams -> hydropower

• reduced risk of flooding

Channelisation in urbanareas

• fast removal of stormwater

• river straightening

• smooth durfaces increase water velocity

• concrete walls

• no or liitle connection to groundwater or surrounding vegetation

higher peak flow

shorter time to peak flow

less infiltration -> lower baseflow

increased likelihood of flooding

difficult to seperate hydrographs (many components: surface runoff, sewer overflow, interflow, fast groundwater flow)

seperate sanitary systems may also overflow due to infiltration through cracks

streams in cities relocated into pipes

effects not fully researched

common in older cities in North America

stream burial decreases hydrological residence times (pipes are smoother) -> increasing flows downstream

strong disconnection of surface water, hyporheic zone and riparian areas

older pipes are leaky

urban kast

pipes surrounded by high-permeable sand and gravel act as preferential flowpaths