Multi-Benefits of Transitioning from Conventional to Sustainable Stormwater Management Approaches

In: Stormwater: Sources, Monitoring and Management 24 October 2019 Nova Publishers Inc, New York Chapter 10 MULTI-BENEFITS OF TRANSITIONING FROM CONVENTIONAL TO SUSTAINABLE STORMWATER MANAGEMENT APPROACHES Ernest O. Nnadi, PhD* Centre for Agriculture, Water & Resilience (CAWR), Coventry University, UK ABSTRACT Sustainable drainage approaches are expanding in function to include water harvesting, water storage and renewable energy. These multifunctions are expected to continue to expand in view of changing climate, water scarcity and rising cost of energy as well as the need to pursue sustainable approaches and resource optimization. This chapter explores the transition from conventional drainage system to sustainable drainage system as well as the multi-benefit applications of sustainable drainage techniques. It appears that the sustainability score card of sustainable drainage systems is also expanding to include other components which are not related to the four pillars of SuDS, but are also sustainable, such * Corresponding Author address: Email: dr.nnadi@gmail.com 2 Ernest O. Nnadi as renewable energy generation and water harvesting. It is expected that these expanding functions would drive increased adoption of the technology even in developing countries. Keywords: Sustainable drainage, renewable energy, water harvesting, stormwater INTRODUCTION Naturally, runoff is not a problem as 95% of rainfall is infiltrated at source and the remaining are evaporated from surface of leaves and soil. However, development of urban areas has increased impervious surfaces reducing infiltration to about 5% with increased runoff during and after rain events resulting in need for drainage systems to deal with runoff. The rise in rural urban-migration as well as world population is challenging for existing infrastructure in the cities and semi urban areas and demanding more developments. Furthermore, in the face of rising world population and climate change, we are witnessing increasing changes to hydrology patterns of cities, rainfall frequency and intensity resulting in frequent flooding events and water pollution. Figure 1 shows the rising number of global natural disasters including flood incidents. In some cases, flooding constitutes a major threat to lives and livelihoods even in rich nations. For example, the cases of flooding incident in Townsville in Australia in February 2019 and the Whaley Bridge flooding in Derbyshire in the UK in August 2019 (which led to evacuation of over 6,800 people from their homes) are demonstrations of the impact of flooding due to changes in weather systems. The impact of flooding in resource poor countries is even worse as they lack early warning and emergency systems to cope with the impact as witnessed in the case of the collapse of Laos dam in Attapeu province in 2018 and India in 2019 which resulted in closure of Cochin International airport. Furthermore, storms and hurricanes are more frequent and their impacts are deverstating, particularly for poor countries. Examples are the Multi-Benefits of Transitioning … 3 case of hurricane Matthew in Haiti in 2016 and recent devastation of Bahamas by hurricane Dorian resulted in loss of lives and infrastructure. The number of these storm events impacts are set to continue to rise and their impacts are expected to be more forecious due to warming climate. The European Academies’ Science Advisory Council report warned that the number of floods and other hydrological incidents have quadrupled since 1980 and increased by 50% since 2004 (EASAC, 2018). The huge cost (Figure 2) of these incidents is putting pressure on countries particularly poor countries already suffering from impact of food shortages and economic crisis. Source: EMDAT (2019): OFDA/CRED International Disaster Database, Université catholique de Louvain – Brussels – Belgium. Figure 1. Frequency of Natural Disasters (including flooding) (Ritchie and Roser, 2019). 4 Ernest O. Nnadi Source: EMDAT (2019): OFDA/CRED International Disaster Database, Université catholique de Louvain – Brussels – Belgium. Figure 2. Economic Cost of Natural Disasters (including flooding) (Ritchie and Roser, 2019). Conversely, there are increased levels of water scarcity, drought and desertification in other areas, even in areas that witnessed flooding during rainy seasons; sometimes experience drought in dry seasons. As rainwater is not harvested during the season of abundant rainfall and stormwater is seen as a problem which needs to quickly removed, there is lack of preparedness to deal with the season of rainfall scarcity. More so, increased in global tourism is putting pressure on tourism industry and governments particularly in developing and transition countries to provide similar facilities as obtainable in developed countries such as swimming pools, gardens, water fountains, etc., with resultant impact on already stretched water resources in these countries. Furthermore, rising urban populations have resulted in increases in the rate of removal of natural vegetation in order to establish urban infrastructures and industries with resultant negative impact urban catchment’s hydrology such as increase in run-off volume and peak flow and increase in the occurrence of dominant discharge. Consequently, there appears to be resultant shift in paradigm, particularly in developed countries from viewing stormwater as a nuisance Multi-Benefits of Transitioning … 5 which should be disposed of quickly to recognising stormwater as a potential resource which can be harnessed, purified, stored and reused to alleviate the problem of water scarcity. This is essentially the high point to any credible stormwater management strategy which should incorporate sustainability component by considering stormwater harvesting and reuse. In the UK, initiatives such water sensitive urban design (WSUD) are attempts to integrate efforts build beautiful and resilient cities with solutions to flood risk, pollution, waste management and improvement of water quality of receiving natural water courses such as rivers and streams (CIRIA, 2018). Similar initiatives exist in some other countries such as the USA and Australia. In the following section, an attempt is made to compare the conventional and sustainable stormwater management systems. CONVENTIONAL VS SUSTAINABLE STORMWATER MANAGEMENT Conventional drainage systems are stormwater conveyance systems designed to remove runoff from source during rainfall events as quickly as possible to receiving natural waters. Hence, they were prone to failure as a result of blockage with high maintenance costs. Also, conventional drainage systems require extensive soil intrusion in order to install gullies and drainage pipes which render the affected areas un-suitable for any other use. Also, conventional urban drainage systems have contributed to the pollution of natural water courses by channelling pollutants carried by stormwater to receiving waters, as well as increasing their temperature leading to distortion of the ecosystem of receiving natural water courses. Furthermore, increase in the number of impervious surfaces used to cover the soil have reduced natural infiltration, increased run-off volumes and have often distorted the natural ecology and landscape of affected areas. Urban runoff is polluted with different kinds of pollutants depending on the environment; and picks up pollution as it travels on surface of soils, 6 Ernest O. Nnadi pavements and drainage channels. This is in addition to rainfall pollution from airborne contaminants which is relatively high in major cities and industrial areas. Some of the contaminants found in stormwater include, microbes, heavy metals, organics such as hydrocarbons (e.g., oil and petrol drips from cars, used lubricants and oils disposed off from garages), pet faeces, dusts and materials from construction and industrial activities, road dusts, plastics, refuse bins, sewerage from bust sewage pipes, fertilizers from farms, food wrappings, pesticides and herbicides, soil particles from excessive soil erosion, farming and forestry activities as well as detergents from car washing and laundry. In cases where stormwater conveyance system is connected to sewerage system (combined sewers), stormwater is polluted with sewerage which increases the volume of flow and pressure on conveyance system as well as increases the cost of treatment and disposal or recycling. More so, conventional drainage systems are not designed to improve stormwater quality, consider environment and deliver amenity, hence stormwater pollution is not treated in situ by these systems and they offer no other benefit except their primary function of stormwater ‘quantity’ removal. In cases where stormwater is allowed to drain into the soil, there could be a risk of groundwater contamination and flooding particularly in areas with low water table and during high rainfall events. Sustainable drainage system is the UK’s equivalent of USA’s Low impact development (LID) of Best Management Practice (BMP) and Australia’s water sensitive urban design (WUSD). SuDS are an array of techniques employed as part of sustainable management strategy to deliver stormwater management at source with regard to the environment. SuDS techniques are different from conventional drainage system as they do not seek to use pipes and channels to remove stormwater runoff from source of rainfall, but rather seeks to control runoff at source as quickly during storm events in order to prevent flooding with minimum environmental impact. The main components of SuDS which are delivered by SuDS techniques are water quantity, water quality, amenity and biodiversity. The four main components of SuDS form what is known as the SuDS square (formerly SuDS triangle with exclusion of biodiversity) or the four pillars of SuDS (Figure 1). SuDS devices include, green roof, biorention ponds, filter Multi-Benefits of Transitioning … 7 strips, filter drains, pervious/permeable pavements, macro pavements, sand filters, retention basins, detention basins, wetlands. SuDS devices such as permeable pavements can be installed in driveways and carparks or housing development; housing estates/complexes; even in city centres, schools/ universities, colleges, hospital, government offices, etc. Furthermore, porous asphalts/ concrete can be installed in industrial estates or shopping malls/ supermarkets and are very efficient in dealing with stormwater runoff at source, detaining and treating stormwater in situ providing ecstatic features and supporting biodiversity. Filter/French drains can be installed at the edge of roads, highways/motorways, even streets to collect, infiltrate, attenuate and treat stormwater. Figure 3. Four pillars of SuDS (Woods-Ballard and Udale-Clarke, 2019). 8 Ernest O. Nnadi Retention and Infiltration basins Multi-Benefits of Transitioning … Swale Porous Pavements &Filter Drain 9 10 Ernest O. Nnadi Porous concrete Porous asphalt Multi-Benefits of Transitioning … 11 Green roof Figure 4. Some SuDS techniques. Rainwater Harvesting The aim of rainwater harvesting is to harvest rainwater in times of plenty for use in times of scarcity, reduce water wastage and encourage optimum water use efficiency in view of rising cost of water supply and global water scarcity. It is estimated that there is about 1.4 billion km3 of water on earth, but only 35 million km3 (2.5%) is fresh water and 24 million km3 (70%) is ice or permanent snow cover (which is melting due to climate change), 30% is groundwater, 105,000 km3 (0.3%) is in freshwater lakes and rivers, and the atmosphere holds about 13,000 km3. Hence, only about 200,000 km3, (which is less than 1% of all the water available on earth) is available for human and ecosystem use (AWF, nd). Hence, water efficiency is an important issue and any means of conserving water should be encouraged. Water availability impacts on all spheres of human 12 Ernest O. Nnadi existence and functions. For example, water sanitation is impossible without availability of water; poverty alleviation, food security and health provision are unachievable without water availability. In Sub-Saharan Africa, there are huge problems associated with water scarcity and these issues cannot be solved until water is made available in these regions. According to the United Nations, an average person requires between 20 and 50 liters (5.3-13.2 gallons) of water each day to satisfy their drinking, cooking, cleaning, and sanitation needs (AWF, nd). Average household water usage in the USA shows that about 61.5% of water supplied to homes is used for indoors (Figure 5). Figure 5. Average household water consumption in the USA (Inskeep and Attari 2014). In the UK, statistics shows that between 2010-2012, water is mostly consumed by households with over six persons (813 litres consumed per day and 123 litres per person) relative to single households (consumes 154 litres per day) and three-person households (consume 421 litres per day) Multi-Benefits of Transitioning … 13 (Statista, 2018). Furthermore, like in the USA (Figure 5), household water usage in England and Wales is mostly for washing and toilet flushing (Figure 3). This indicates that water can be saved by rainwater harvesting using SuDs devices which can supply water fit for most of these uses and ease the burden on the portable water. More so, the technology for harvesting water using SuDS devices have been perfected and can be applicable in developing countries and third world countries were water scarcity is threatening lives and economies, exacerbated by rising populations in these regions of the world, climate change and drought conditions which are threatening food supply especially during dry seasons. A simple household rainwater collection system is shown in Figure 7, but Sustainable drainage techniques such as permeable pavements (Figure 8) could also be used to treat and harvest stormwater for wide range of uses to meet household water requirement and improve on water efficiency. The British Standard BS 8515:2009 regulates the design, installation, water quality, maintenance, and risk management of rainwater harvesting systems. Figure 6. Average household water consumption in the England & Wales (EPA 2010). 14 Ernest O. Nnadi Figure 7. A simple household Rainwater Harvesting System (Armstrong et al., 2017). Rainwater harvesting can help to improve food availability by application as irrigation fluid in gardens, landscaped areas and greenhouses. SuDS devices can be engineered to provide added benefit of water storage for reuse as irrigation fluid (Nnadi et al., 2015). Studies have shown that use of harvested and treated stormwater runoff via SuDS devices does not pose any danger to human or animal health and does not impact negatively on soil structure if used as irrigation fluid (Nnadi et al., 2013; Nnadi et al., 2015). Harvested stormwater can be applicable in residential areas (such as for toilet flushing , hand washing, clothes washing, etc) and industrial settings, agriculture, water displays such as decorative ponds and water fountains, replenishment of aquifer, roof and ground gardens. Also, rainwater harvesting can encourage urban agriculture in the cities and can be extended to other areas. Figure 9 shows tomato and rygrass plants after 10 weeks of irrigation on harvested and treated stormwater in SuDS device – permeable pavements (Figure 8). Multi-Benefits of Transitioning … 15 Figure 8. Stormwater Treatment Using Permeable Pavement System (PPS). However, some of the microbes found in stormwater can be pathogenic and hence, there is need for effective treatment system if reuse option is being considered as the risks associated with microbial pollution of stormwater are normally considered to be higher. Pathogens found in water recycling application are mostly enteric in nature and enter into the stormwater or stored water through faecal and sewage contamination from agricultural soil and livestock manures from adjoining areas. These organisms include: bacteria, protozoa, helminthes and viruses, but they do not normally persist in SuDS systems such as PPS due to unfavourable environmental conditions and competition with indigenous microbes which are more adaptable to the environment. However, enteric organisms which could pose a huge risk to humans and animals could be dispersed through irrigation water sprays on harvested plant parts (such as leaves and fruits). Hence, care must be taken to ensure that the risk of contamination is eliminated (even during storage) and that effective monitoring process is put in place. 16 Ernest O. Nnadi Figure 9. Tomato and ryegrass irrigated with harvested and treated stormwater in SuDS device. Renewable Energy Generation Pavements can offer added benefit of serving as a generator of renewable energy. Wide range of technologies are available and some are been considered for application for this purpose. Conversion of geothermal energy using Ground heat pump system (GHPS) installed in pavements for application in residential buildings and offices have been reported. For example, Coupe et al. (2014) and Charlesworth et al. (2017) reported installation of combined water harvesting and ground heat pump system at Hanson Eco-House at BRE (Figure 10), Watford, UK and Hanson Stewartby Offices in Bedford UK. Balbay and Esen (2010) showed that GHPS could be used successfully to melt snow on pavements and decks. There are reports of using pavements to harvest solar energy for application in charging mobile phones (Figure 11), recharging electric cars and providing energy supplies to offices (Jungblunt 2018). Multi-Benefits of Transitioning … Figure10. Hanson Eco-House at BRE Technology Park, Watford https://www.bregroup.com/ipark/parks/england/buildings/the-hanson-ecohouse/ Figure 11. Recharging mobile phone on deck in Budapest (Jungblut, 2018). 17 18 Ernest O. Nnadi In another case, a pavement are covering about 4.7 square meters, are built into the sidewalk near Prologis Park Budapest-Harbor’s electric car charging station in Budapest (Figure 12). Figure 12. Prologis Electric Car Charging Station powered by energy from pavements (Budapest Business Journal, 2018). The installation generates sufficient energy to provide the electric charging station with energy to recharge cars and diverts the energy to supply electric power to nearby offices when the electric car charging station is empty (Budapest Business Journal, 2018). Another example is one-kilometer solar road (Figure 13) constructed at the cost of €5m and installed with 2,880 solar panels opened to motorists in 2016, in Tourouvre-au-Perche, Normandy, France with capacity to generate energy to power street lighting in the village of 3,400 residents. In Netherlands, a cycling path in the town of Krommenie near Amsterdam was installed with solar energy collecting system which generated about 9,800 kWh in its first year of operation and the project has been expanded to generate more energy (van Rooij, 2017). Multi-Benefits of Transitioning … 19 Similar project have been installed in other places in the world such as Idaho USA, green energy generating side walk Missouri, USA and solar energy collector paved road in Shandong province in China. Figure 13. One Km solar road in Tourouvre-au-Perche, France https://www.theguardian.com/environment/2016/dec/22/solar-panel-road-tourouvreau-perche-normandy. Figure 14. Solar energy generating cycle path in Netherlands (van Rooij, 2017). 20 Ernest O. Nnadi Figure 15. Express way section paved with solar panels in Jinan, Shandong province, China. https://www.telegraph.co.uk/china-watch/technology/first-solar-panel-road/. Thermal collector pavements which involved collection of solar energy from pavement surfaces and transmission through fluids placed in pipes or tubes underplayed in the pavement can help to reduce the impact of heat from pavements on the pavement structure (reducing wear and tear) and receiving waters, particularly in a case where runoff is channelled to receiving natural waters (Papadimitriou et al., 2019). The Federal Highway Administration of US department of transportation is exploring the potential of harvesting energy from road and pavements through kinetic – to-electric conversion (KEEC) system exploiting the accumulation of electric charge in solid materials when exposed to force or stress (USDT, 2019). In all these and other cases, sustainable stormwater management devices are providing added benefits in addition to their primary functions and these appears to be driving their adoption and installation in wide range of cities in the world. Multi-Benefits of Transitioning … 21 CONCLUSION Sustainable drainage techniques (such as permeable pavements system) offers great opportunity for water harvesting for wide range of low range uses which can alleviate the water usage burden on portable water supply, where they are available and functional, and where they are not, or mostly inefficient, installation of SuDS devices can form an essential water supply strategy for water provision. Such application can alleviate water scarcity, support biodiversity, encourage food production, reduce effect of urban heat island and deliver improved water quality, recharge of groundwater system as additional benefits to their sustainable drainage function. Furthermore, the technology can be incorporated into new developments designs and can easily be retrofitted into existing developments and infrastructure. It is clear that the application of drainage systems such as pavements have expanded to include renewable energy generation and many cities are exploiting this benefit by constructing green energy harvesting systems using pavements. It is expected that these added benefits and multi-functional roles of sustainable drainage approaches would continue to expand, driving my advances in technology, need to optimise use of resources and the sustainability component. REFERENCES Armstrong, A., Bartram, J., Lobuglio, J., Elliott, M. (2017) Rainwater harvesting from rooftops https://www.climatetechwiki.org/content/ rainwater-harvesting-rooftops. AWF (nd) How Does Water Use in the United States Compare to That in Africa? https://www.awf.org/blog/how-does-water-use-united-statescompare-africa Balbay, A. and Esen, M. 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