An approach to mitigating flash flood

Introduction

Nowadays, flash flood have become major thread towards the environment and development, same goes with Bercham, a sub -urban area located at Hulu Kinta district, Ipoh, Perak. Bercham is the lowest point in Ipoh Perak. In this context, this chapter briefly explain the inter connection of flash flood mitigation approach, the used of river as centre of community area and the used of river as point of connectivity. This chapter also attends other’s site that facing almost the same issues and the mitigation approach that they used.

Furthermore, in this chapter also highlight the principles and idea not only for mitigating flash flood but also an approach to.

Literature Review

Linear Park

Linear Park can be considered as one of the public space . In a scope of urban context, linear park was proposed as public gathering area that merge well with linear margin of urban development. To be more precise, the purpose of linear park is to provide long -term direction for the planning and construction for creating well -coordinated, sustainable and environmentally trail network connecting spaces sprawling throughout the city.

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It is also to provide recreational opportunities and accommodate alternative transportation for diverse range of trail users for example pedestrians and cyclists. (Linear Parks Master Plan , 2009)

Flash Flood

A flood is defined as water overflowing onto land that usually is dry. Flooding is often thought of as a result of heavy rainfall, but floods can arise in a number of ways that are not directly related to ongoing weather events.

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(Planning Institute of Australia, 2009) . Flash floods are defined as those flood events where the rise in water is either during or within a few hours of the rainfall that produces the rise.

Therefore, flash floods occur within small catchments, where the response time of the drainage basin is short. (Planning Institute of Australia, 2009) For most people flooding implies harm; however, flooding also has economic and environmental benefits (Green, 2010). In VMD, seasonal flooding is a critical development resource (Ehlert, 2012). It serves as a source for agricultural irrigation and domestic water uses, increases wild fishery resources, brings alluvium to fertilize farmlands, washes out salt s and toxins from the sulphate soils, carries away wastes, eliminates rats and insects, and recharges groundwater (Biggs, 2010; Brocheux, 1995; Le, Hoanh, Miller, & Sinh, 2007). The Vietnamese term for ‘flood season’ is translates directly as ‘rising -water season’ (Le, Hoanh, Miller, & Sinh, 2007). Far from harmful, the flood usually comes and goes very slowly that a local farmer likened it to a turtle (Ehlert, 2012). Fishermen consider the flood season as “income season” because it brings extra fish in the flooded field, implying the flood as a friend (Nguyen & Alexander, 2014).

Different floods are clearly differentiated (Le, Hoanh, Miller, & Sinh, 2007). A moderate flood (l?u v?a) is also called ‘beautiful flood’ (l?u) because it brings livelihood resourc es. A small flood (l?u nho?) and a high flood (l?u l?n) are undesirable, for the former results in less fish and promotes weed infestation in the field after the flood and the latter can lead to disasters (Danh & Mushtaq, 2011; Ehlert, 2012; Nguyen & Alexa nder, 2014).

Urban Flood Resilience

Not all floods can be prevented but their impacts can be reduced; this is the current thinking in flood risk management, endorsed by the EU’s Floods Directive. It represents a shift from conventional forms of flood management which attempt to avoid flooding using physical infrastructure, such as barriers.

Cities must become more prepared for floods, because climate change, population growth and urbanisation are changing the causes of flooding and increasing its impa cts. (Liao, Le, & Nguyen, 2016)

  1. Resistance – the ability of a neighbourhood to reduce damage to its major infrastructure (neighbourhood components that are essential to oper ation).
  2. Absorption – the ability of a neighbourhood to operate despite damage to major infrastructure. This usually involves the provision of alternative systems, if one system stops working.
  3. Recovery – the ability of a neighbourhood to bring major infra structure back into operation.

Thirsty Landscaping Approach

Thirst landscaping is derived from two basic words which are “Thirsty” and “Landscape”. Thus definition is as follow:

Thirsty

  • A sensation of dryness in the mouth and throat associated with a desire for liquids also : the bodily condition (as of dehydration) that induces this sensation
  • A desire or need to drink (www.merriam -webster.com)

Landscape

Forman and Godron (1986) defined landscape as a heterogeneous land area composed of a cluster of interacting ecosystems that is repeated in similar form throughout. Turner et al (2002) define landscape as an area that is spatially heterogeneous in at least one factor of interest.

Thus, t hirsty landscaping can be define as an open space or area designed focus on taking in water element into the space and utilise it for further purposes. This include through water absorption, filtration or penetration from any area into the focus site and i dea.

References Cases

Selected reference case study assist on identifying the sites issues and mitigation approach and design for mitigate the effect of flash flood in Bercham, Perak. The selected reference cases comprise from neighbouring country for int erpreting the approach and solution used to be implemented at Bercham, Perak .

Bangkok Fight Flood with Thirsty Landscape

Site Background

The origin of the Chao Phraya River is the confluence of the Ping, Wang, Yom and Nan rivers about 200 km north of Bangkok. From Nakhon Sawan, the river flows through the central plain passing Bangkok toward the Gulf of Thailand. At Ayutthaya about 55 km No rth of Bangkok, the Chao Phraya river is joined by the Pasak river which rises in the divide between the central alluvial plain and the North -east plateau. The Lower Chao Phraya river basin starts from Nakhon Sawan and has a drainage area of 21,725 km2 the average annual precipitation is 1,487.3 mm and the average discharge at Sang Khla Buri District, Chainat Province has been 117.0 m3/s. Chao Phraya reservoir built in 1957 is the largest existing reservoir in this basin. (Chao Phraya River , n.d.) The city, once a network of canals that earned it the moniker “”Venice ofthe East,” has filled in many of those water channels for co nstruction, and is sinking by more than 1 centimeter (0.4 inches) each year, according to climate experts.

Issues and Problems

Due to poor water management system. Rapid city of Bangkok urbanization, lack of impervious surfaces, and heavy seasonal monsoon rain.

Design Approach es and Solutions

a) Green Avenue – 1.3km green avenue connecting Chulanglongkorn University with com mercial area. The long green avenue function to collect and treat surface water run -off , thus decrease the flood risk. Other function is to mitigate urban heat island effect. The green avenue also promote pedestrian and bicycle movement and transportation.

b) Centennial Park -located A “”metro forest”” project in a Bangkok suburb has converted two acres (0.8 hectares) of abandoned land into a local forest with native trees, to make a start on reversing urban sprawl. The park act as retention pond. The city’s 11 -acre Chulalongkorn Centenary Park designed by Kotchakorn is inclined at a three -degree angle, so that rain and floodwater flow to its lowest point, into a retention pond. At the park’s highest end, a museum is topped by a green roof covered with native pl ants, which filter rainwater before it is stored in large tanks underground. Rainwater also flows through the park’s lawn and wetlands where native vegetation filters the water, while its walkways are made of porous concrete. The park can hold up to 1 mill ion gallons of water that can be discharged later or used in the dry season, much like a monkey holds food in its cheeks until it needs to eat, said Kotchakorn, echoing an idea of Thailand’s revered late King Bhumibol Adulyadej to contain flooding in the city.

Bishan – Ang Mo Kio Park From Concrete Canal to The Natural Wonderland

Site Background

Singapore is an island city -state located at the very southern tip of the Malaysian peninsula. Formerly a British colony, Singapore became part of Malaysia in 1963, and then became fully independent in 1965. Singapore is relatively small in size with an area of about 700 square kilometers, approximately three and a half times the size of Washington D.C. (Central Intelligence Agency, n.d.). The popul ation is rather large, with over 5 million people (Central Intelligence Agency, n.d.), thus development in the city -state is very dense. Traditionally, development has occurred in such a way as to separate the more wild areas from the developed ones, confi ning the “wild” to nature reserves such as Bukit Timah. Many open spaces throughout the housing areas are well manicured and covered with lawns. Singapore has a wet and tropical climate, and receives significant amounts of rain each year approximately 2,40 0 mm. However, Singapore has not yet been able to capture a sufficient amount of rainwater to meet its water demand when coupled with its other domestic water sources (Dreiseitl, 2007). Thus, Singapore currently imports 40% of its water from Malaysia, a si tuation Singapore would like to change (Dreiseitl, 2007).

Currently Singapore describes its water supply through the idea of four national taps: imported water from the Johor River (purchased from Malaysia), desalinated water, NEWater (a technology that pu rifies and recycles water), and local catchment water (PUB, Singapore, 2013b). If imported water makes up 40% of the supply, approximately 20% comes from local water catchments, which now make up two -thirds of Singapore’s lan d area (PUB, Singapore, 2013b).

With so much rain, and so much developed land, risk of flooding is high. Throughout the first decades of independence, Singapore set up a sophisticated drainage system to move water as quickly as possible away from development and into the ocean through a vast network of concrete canals and drains. This system is currently made up of 32 rivers, 17 reservoirs, and over 8,000 kilometers of waterways (PUB, Singapore, 2013b) .

Bishan Ang Mo Kio Park

The 62 -hectare Bishan -Ang Mo Kio Park, first opened in 1988, is located between the two housing estates of Bishan and Ang Mo Kio, in the

central area of the island. It is located north of the Central Business District and just east of the Central Water Catchment, next to the Lower Pierce Reservoir. It is about one -sixth the size of Central Park, or about twice the size of the Boston Common and Public Garden combined (Central Park Conservancy, 2014; Friends of the Public Garden, n.d.). It is enclosed on its northern edge by Ang Mo Kio Avenue 1, on its southern edge by Sin Sungai P inji, Bercham Perak.

Ming Ave and Bishan Street 22, on its eastern side by Bishan Road, and on its western side by Upper Thomson Road. Marymount Road bisects the park. It is surrounded by high density residential developments. The Kallang River, which runs for 10 kilomete rs from the Lower Pierce Reservoir to the newly completed Marina Reservoir, originally ran through the park for 2.7 kilometers in a straight concrete channel along the Southern edge of the park, blocked off from people by fences (“Cities of the Future,” 20 12). Despite the barriers, the canal still attracted residents, especially children, who would climb into the canals to play. Once someone was in the canals, the fences made it difficult to exit, sometimes dangerously trapping children in the canals with r ising water levels (Dreiseitl, 2012).

The park was and remains very popular, attracting over three million visitors annually (Rinaldi, 2013). By the early 2000s, it was in need of significant maintenance and repair especially with regard to drainage proble ms and the concrete canal, parts of which were crumbling (Rinaldi, 2013). Thus, as part of the ABC Waters Programme, this park was slated for redesign. PUB and Singapore’s National Parks Service (NParks) teamed up with the design firm Atelier Dreiseitl and the engineering firm CH2M HILL to redesign the park. Both firms had been involved with carrying out the Central Catchment Area Master Plan.

While there are many intriguing aspects of the redesign of Bishan Ang Mo Kio Park, completed in March 2012, this pa per focuses on the use of natural processes and materials to provide flood control, erosion control, water purification, and water filtration, and the community’s interaction and engagement with the park.

Issues and Problems

Flood

While the concrete canal that was originally in the park may not have seemed pleasant or aesthetically nice, it was functional. Kallang River was engineered into a concrete canal to efficiently convey storm water from the rapidly urbanizing satellite towns of Bishan and Ang Mo Kio in the 1960s. In 1988, the park was built around the canal but the two were never fully integrated because concrete canals convey water at high velocities during storm events but were also a safety hazard during periods of ra in” (“Kallang River Bishan Park,” 2014). The redesign sought to keep the functionality, but also to bring the river into the park, where park goers could easily and safely interact with the water.

Design Approaches and Solutions

Flood Co ntrol

Rather than another 24 -meter wide concrete channel, the new design is based on the idea of using the parkland to serve as a flood plain (Rinaldi, 2013). When little water is running through the river, the riverbanks, which are covered in vegetation and grass, provide recreational areas. When water levels are high, the surrounding parkland is inundated and serves as flood zones. During these times, most people would not be in the park anyway, so the limited parkland is not an issue (Dreiseitl, 2012). This new design not only allows for multiple uses of the space in the park, with more opportunities for park goers to interact with the water, but it also provides even greater flood prevention, with the ability to carry 40% more water than the previous ch annel (“Kallang River Bishan Park,” 2014). The meandering of the river lengthened the channel in the park from 2.7 kilometers to 3.2 kilometers. The longer course helps slow the flow of water through the park, aiding in water treatment, filtration, and saf ety (Rinaldi, 2013).

Concern over water safety fueled a debate about incorporating barriers into the redesigned river as there had been previously. “‘The biggest challenge we had to face as designers, up until the final stages of the project, was fear of water,’ Dreiseitl says” (Rinaldi, 2013, p. 87). Rather than constructing fences or barriers to the river, however, the designers worked with the government to engage the public in the creation of a river monitoring and warning system. The system is compris ed of red markers throughout the park that show where the maximum water levels are and hence indicate safe higher ground. When sensors detect that water levels are rising rapidly, threatening the safety of park goers, warnings are issued via loudspeakers a nd flashing lights. There are also warning signs throughout the park in multiple languages, reflecting the many languages spoken in Singapore (Rinaldi, 2013).

Creating what looks like a natural river required a lot of engineering and planning. When the channel was made of concrete, riverbank erosion was not a concern. A naturalized river with soil riverbanks has to protect its riverbanks against erosion. In order to maintain the natural and green aesthetic of the river, but ensure that the banks of the r iver would not suffer from erosion during floods, the designers tested and employed soil bioengineering techniques.

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An approach to mitigating flash flood. (2019, Dec 10). Retrieved from https://studymoose.com/an-approach-to-mitigating-flash-flood-essay

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