River restoration and conservation in damaged urban catchments
River restoration is the process of managing previous damaged rivers to reinstate natural processes to restore biodiversity, providing benefits to both people and wildlife. It has been needed due to the huge amount of damage done to urban rivers and the increasing awareness that drainage systems provide lots of amenity services to people and the environment.
River restoration is part of river conservation, the protection, preservation, management, or restoration of wildlife and of natural resources such as forests, soil, and water. This can be observed on the photo opposite of the River Skerne, Darlington, restored between 1995 and 1998.
The restored River Skerne in Darlington 1
The Cheonggyecheon River Restoration Project, Seoul, South Korea
Seoul is the capital and largest city in South Korea. It is situated in the northwest part of South Korea on the Han River which roughly bisected into northern and southern halves. It is one of the world’s largest cities with a population of 10,197,604 million people (2017).
The sprawling metropolitan area is much larger at 24.5 million people – the 5th most populous in the world. It is also noted for its population density (17,000 people per km2), which is almost twice that of New York and eight times greater than Rome.2
Cheonggyecheon is a small region in a central area of the city. It contains the Cheonggyecheon River, which had been badly damaged in the past and was restored from 2003. The restoration was needed because of decades of human alteration of the river;
1918 – The Japanese administration dredge sediments out of the river and aimed to cover it over as the stream was viewed as a health and flood risk. Work halted because of the second World War
1958 to 1961 – the Cheonggyecheon stream was completely covered over
1971 - An Expressway was built that totally covered the river and prevented evapotranspiration, damaged river flows and enclosed the river system.
These changes had a major impact upon the water balance in this damaged urban catchment;
The plan of the restoration scheme5
The river Restoration project.
In 2003 a river restoration project was launched to bring environmental benefits back to the river. The overall aims were for;
The total length of the restored area is 5.8 km within an area of approximately 1,000 acres. This whole area has been turned into a green strip that is very beneficial for the citizens of Seoul. The cost of the restoration scheme was $281million.3
The restored river - Nesnad [CC BY-SA (https://creativecommons.org/licenses/by-sa/3.0)]6
Features of the scheme included;
Cheonggyecheon before the reconstruction (2001, left) and after the reconstruction (2005, right) 7
Impact on the Urban RIVER Catchment
a) Flow rates within the river were maintained at a constant rate - 120,000 tons of water are pumped in daily from the Han River, its tributaries, and groundwater from subway stations.
b) Provides flood protection for up to a 200-year flood event and can sustain a flow rate of 118mm/hr
c) Biodiversity Increased by 639% between the pre-restoration work in 2003 and the end of 2008 with the number of plant species increasing from 62 to 308 and fish species from 4 to 25.
d) Reduction in average air temperatures by 2.5°C as a result of reducing the number of cars and reintroducing plants. This reduces the urban heat island effect.
e) Evapotranspiration rates increased because of the introduction of plants to the system. f) Alteration to the inputs to the system, with added water from the Ham River and rainwater now present
g) Biological oxygen supply improved via small waterfalls
NEXT TOPIC -Urban Physical Waste Generation
1- The river restoration centre (1998) – The River Skerne. Accessed 11th January 2020 at https://www.therrc.co.uk/pdf/Publications/skerne_brochure.pdf
2- Just fun facts (2018). Seoul, Accessed 11th January 2020 at http://justfunfacts.com/interesting-facts-about-seoul/
3- - Newcastle University Blog – no longer available. http://2014-2015.nclurbandesign.org/uncategorised/cheonggyecheon-river-restoration-project-restoration-environmental-social-economic-seoul/
4- Wikipedia – Cheonggyecheon. Accessed 11th January 2020 at https://en.wikipedia.org/wiki/Cheonggyecheon
5- Landscape Architecture projects (no date provided). Cheonggyecheon Stream Restoration Project. Accessed 11th January 2020 at https://landscapeperformance.org/case-study-briefs/cheonggyecheon-stream-restoration
6- Nesnad [CC BY-SA (https://creativecommons.org/licenses/by-sa/3.0)] Accessed 12th January 2020 at https://commons.wikimedia.org/wiki/File:Cheonggyecheon_shortly_after_reopening_-_oct_9_-_2005.jpg
7- Philipp, Conrad & Wannous, Joullanar & Pakzad, Parisa. (2015). Thermal impact of blue infrastructure: Casestudy Cheonggyecheon, Seoul (Korea). Accessed 12th January 2020 at https://www.researchgate.net/publication/283523783_Thermal_impact_of_blue_infrastructure_Casestudy_Cheonggyecheon_Seoul_Korea/citation/download
Posted by Rob Gamesby April 2020