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Wastewater is water that after use for life support, industrial processes, or life enhancement must be ..... Houghton Mifflin Company, Boston. Buerger, C. (1915).
Historical Perspectives of Urban Drainage Steven J. Burian* and Findlay G. Edwards* *Assistant Professor, Dept. of Civil Engineering, University of Arkansas, 4190 Bell Engineering Center, Fayetteville, AR 72701 USA, Phone: (479) 575-4182; [email protected] / [email protected]

Abstract Historically, urban drainage systems have been viewed with various perspectives. During different time periods and in different locations, urban drainage has been considered a vital natural resource, a convenient cleansing mechanism, an efficient waste transport medium, a flooding concern, a nuisance wastewater, and a transmitter of disease. In general, climate, topography, geology, scientific knowledge, engineering and construction capabilities, societal values, religious beliefs, and other factors have influenced the local perspective of urban drainage. For as long as humans have been constructing cities these factors have guided and constrained the development of urban drainage solutions. Historical accounts provide glimpses of many interesting and unique urban drainage techniques. This paper will highlight several of these techniques dating from as early as 3000 BC to as recently as the twentieth century. For each example discussed, the overriding perspective of urban drainage for that particular time and place is identified. The presentation will follow a chronological path with the examples categorized into the following four time periods: (1) ancient civilizations, (2) Roman Empire, (3) Post-Roman era to the nineteenth century, and (4) modern day. The paper culminates with a brief summary of the present day perspective of urban drainage. Introduction The relation of modern engineering to ancient engineering is difficult to comprehend considering that modern engineering is so highly specialized and technologically advanced. Design rules-ofthumb, empirical equations, physics, numerical methods, computer simulators, and other engineering tools taken for granted today were not available to ancient engineers. Despite the supreme technological advantage today’s engineer has over the ancient engineer, fantastic engineering feats rivaling those of today were achieved throughout history. For example, several ancient civilizations built magnificent cities of stone, brick, and wood and equipped the cities with sophisticated infrastructure systems including roads, water supply and distribution systems, wastewater collection, and stormwater drainage. Further, in some instances infrastructure systems were integrated, as was often the case with wastewater collection and stormwater drainage. Urban drainage is defined to include two types of fluids: wastewater and stormwater (Butler and Davies 2000). Wastewater is water that after use for life support, industrial processes, or life enhancement must be collected and disposed of appropriately to prevent nuisances and polluted conditions from developing in urban areas. Stormwater is runoff produced by precipitation. Both wastewater and stormwater must be considered during urban drainage system planning. Historically the two waters have either been combined into a single conduit (i.e., combined 1

sewers), or have been kept separate during collection and disposal (i.e., separate sewers). Both combined and separate urban drainage systems will be discussed in this paper. This paper will explore the perspectives of urban drainage that have prevailed throughout history. According to the Merriam-Webster Dictionary, perspective is defined as the interrelation in which a subject or its parts are mentally viewed. Using this definition we reviewed historical accounts of urban drainage systems and formed an opinion of the prevailing perspective of urban drainage for that time period and location. We found that urban drainage has been viewed as a vital natural resource, a convenient cleansing mechanism, an efficient waste transport medium, a flooding concern, a nuisance wastewater, and a transmitter of disease. Urban drainage systems were planned, designed, built, and retrofitted in response to the prevailing view of urban runoff. Ancient Urban Drainage Systems "The history of man is reflected in the history of sewers…" -Victor Hugo, Les Misérables Historical accounts of ancient civilizations (e.g., Indus and Minoan) suggest urban drainage systems were constructed with great care and that the objectives of the systems were to collect rainwater, prevent nuisance flooding, and convey wastes. The systems that eventually met their objectives likely did so after trial-and-error modifications. In general, planning and design were limited. Few numerical standards existed for urban drainage and engineering calculations were not used during design. Despite the lack of optimization and the use of trial-and-error construction methods, numerous ancient urban drainage systems can be rated very successful. Lewis Mumford summarized the state of ancient urban infrastructure when he stated that ancient sewer systems were an “uneconomic combination of refined technical devices and primitive social planning” (Mumford 1961). The Indus civilization flourished in the Indus River Valley during the beginning of the third millennium BC. Webster (1962) and Kirby et al. (1956) described the technologically advanced urban drainage systems that the Indus civilization constructed for several of their more important cities. Ruins from two cities in particular provided a detailed glimpse of the Indus urban drainage systems. The ruins from Harappa and Mohenjo-Daro, two Indus cities separated by about 350 miles, suggest that they were arranged according to a plan and that the urban drainage system was coordinated with the layout of the town sites. Connections were built from most residences to open channels constructed in the center of the streets. The channels were either excavated into the ground or constructed above ground of burnt brick (see Figures 1 and 2). Although houses were connected to the drainage channels, wastewater was not permitted to flow directly to the street sewers. First, the wastewater was passed through tapered terra-cotta pipes into a small sump. Solids settled and accumulated in the sump, while the liquids overflowed into the drainage channels in the street when the sump was about three-fourths full. The drainage channels could be covered by bricks and cut stones, which likely were removed during maintenance and cleaning activities. Another interesting feature of the channel was the inclusion of a cunnette (Webster 1962). The cunnette was probably constructed to convey the smaller

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flows associated with daily wastewater discharges, while the entire channel would only be used during wet weather events. Overall, the Indus civilization viewed urban drainage systems as providing the dual purposes of waste and stormwater conveyance.

Figure 2. Picture of Harappan above ground sewer channel constructed of burnt brick (Kirby et al., 1956) Figure 1. Picture of Mohenjo-Daro excavated sewer channel (Hodge, 1992)

The Persians were another ancient civilization that constructed urban drainage systems. Niemczynowicz (1997) explained that ancient Persians considered urban runoff sacred and enacted laws to protect it from pollution. Polluting water in Persia was considered a sin. Moreover, rainwater and urban runoff were collected in cisterns for potable uses. Deep wells injected urban runoff into the underlying aquifer. The Persian perspective of urban runoff was clearly as a vital natural resource. Unfortunately, as time passed changes in the Persian attitudes and behavior contributed to water pollution problems and the eventual downfall of the civilization (Niemczynowicz 1997). The Mesopotamian Empire states of Assyria and Babylonia marked great advances in civilization during the second millennium BC. The ruins from Mesopotamian cities contain well-constructed storm drainage and sanitary sewer systems. For example, the ancient cities of Ur and Babylon, located in present day Iraq, had effective drainage systems for stormwater control (Jones 1967). The systems contained vaulted sewers and drains for household waste and gutters and drains specifically for surface runoff (Maner 1966). The material of choice was baked brick with an asphalt sealant. Rainwater was also collected for household and irrigation uses. The Babylonians were partially motivated to construct urban drainage systems by their desire to remain clean. The Babylonians, like other ancient civilizations, viewed uncleanliness as a taboo, not because of the physical uncleanness but the moral evil it suggested (Reynolds 1946, pp. 198-204). In retrospect, the Mesopotamians viewed urban runoff as a nuisance flooding concern, waste conveyor, and a vital natural resource.

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The Minoan civilization flourished on the Island of Crete from about 2800 BC to 1100 BC. The ruins from this civilization located on the Aegean Sea revealed elaborate systems of well-built stone drains (see Figure 3), which carried sanitary sewage, roof runoff, and general surface drainage (Gray 1940). The drains emptied into a main sewer that disposed of the sewage a considerable distance from the origin of the wastes. The frequent and torrential rains in Crete resulted in excellent flushing of the system. Ruins from the palace-city of Knossos indicate that a two-conduit system was installed, where one conduit collected sewage and the other rainwater. The efficient separate urban drainage system integrated with rainwater collection devices suggests that the Minoans viewed urban runoff as a nuisance flooding concern, a waste conveyance mechanism, as well as a vital natural resource.

Figure 3. Minoan storm drain at Knossos dating to 1500 BC (Daedalus 2002, used with permission).

The Etruscan civilization built some of the first organized cities in central Italy around 600 BC (Scullard 1967). Marzobotto, one of the more important Etruscan cities, had a skillfully designed drainage system making use of the natural slope to keep the city dry and clean. In addition, paved streets and stepping-stones in the roadways acted as protection for pedestrians against stormwater runoff (Strong 1968). The Etruscans, similar to other ancient civilizations, formed the perspective of urban runoff as a nuisance flooding concern, a waste conveyor, and a vital resource. We do not have enough space to thoroughly review every example of ancient urban drainage systems. Other civilizations, most notably the Egyptians, Hittites, Greeks, and Chinese also constructed well-planned urban drainage systems. Although we will not review them we can state that their perspectives of urban drainage were similar to the perspectives exhibited by the other civilizations that we did review in that they viewed urban drainage as a nuisance flooding and pollution concern, a waste conveyance mechanism, and a vital natural resource.

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Urban Drainage Systems in the Roman Empire Preceding, during, and shortly after the Roman Empire significant urban drainage technological advances were introduced. Noteworthy examples include the development of uniform roadway drainage practices and the construction of large underground conduits linked to form an intricate network of sewers. The following discussion will illustrate the overriding Roman perspective of urban drainage to be flood mitigation and drainage of lowlands, but the collection of rainwater for household and public use was also considered important. The Romans were the only civilization in all of western Asia and Europe from antiquity to the 1800s to build a carefully planned road system with properly drained surfaces (Hill 1984). Adequate roadways were constructed during the period of Etruscan domination in Italy (800-350 BC), but these roads were not as intricate as the Roman roads, nor were the drainage systems as carefully planned. When the Romans came to power they rebuilt and expanded many of the Etruscan sewers and paved streets. Along some roadways they implemented curb and gutters to direct surface runoff to rock-lined open drainage channels (Hill 1984). Many of the roadbeds were graded to direct the surface runoff from the streets toward the drainage channels. In addition to the urban drainage component incorporated into roadway design and construction, the Romans used rainwater collection extensively in their drainage system. Typically rainwater falling onto an urban area would be stored for local use. Rainfall on rooftops was often collected into a cistern located in the interior of the house (Hodge 1992). Figure 4 shows a picture of one of the massive underground structures built to store water draining from a large area.

Figure 4. Picture of a Roman cistern in Fermo, Italy.

The construction of an efficient urban drainage system was motivated by the need to drain the low-lying districts, to dispose of urban stormwater runoff, and to remove the excess water 5

imported into the cities via the aqueducts. Shortly after construction of an aqueduct water would overflow from street fountains and public baths because all of the water being imported was not being consumed (Hodge 1992). To meet the urban drainage needs an intricate network of open channels and underground sewers, or cloacae, was constructed. The largest of the cloacae was called the Cloaca Maxima, which drained the lowest parts of Rome about the Forum into the Tiber River (Gest 1963). The Cloaca Maxima usually contained a significant flow of water from the low-lying swamplands, which provided a convenient medium by which to transport wastes. Residents in populace areas of the Roman Empire took advantage of the constant flow in the open channels and underground sewers to transport their wastes away from their living areas. Although not by design, the Romans produced a linkage of urban water supply and urban drainage by way of the aqueduct overflow into the sewers. The Roman linkage of the urban water supply and drainage systems marks one of the earliest examples of establishing an urban water cycle. Previously, other civilizations (e.g., the Minoans) had constructed water distribution and urban drainage systems in the same city, but not to the scale of the Romans. The urban water cycle became common during the late nineteenth century in Europe and the United States with the widespread construction of piped-in water supplies and water-carriage sewer systems (Burian 2001). Urban Drainage Practices from the Post-Roman Era to the 1800s "The sewer is the conscience of the city." -Victor Hugo, Les Misérables Following the fall of the Roman Empire, cities in most of Europe and parts of Asia began to shrink considerably as residents migrated away from the urban centers (Bishop 1968). The population reduction of the cities resulted in the abandonment of municipal services, e.g., sewer systems, running water. The neglect of these systems contributed to their deterioration. Another factor that contributed to the demise of urban drainage systems during this time period was the general apathy and indifference of urban residents during the Dark Ages time period. If people neglected their own cleanliness how could they be expected to be concerned with the cleanliness of the community? During the Dark Ages few technological advances were made, let alone implemented, in Europe. Consequently, urban infrastructure elements including urban drainage systems were not being improved. The prevailing public perspective of urban drainage during this time period was an unneeded service. In Medieval Europe, urban drainage practices were limited because most people lived close to streams, rivers, or other bodies of water. Residence close to waterways was required because water was not commonly brought into the urban area via aqueducts or pipes as had been done in antiquity. Urban stormwater runoff and industrial (e.g., tanners and dyers) wastewater were the primary waste discharges into local streams and rivers. Human feces were collected and used in backyard gardens. Other garbage and household trash were typically stockpiled near the city or fed to pigs.

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The sewers implemented in Europe following the fall of the Roman Empire were simply open ditches, essentially reverting to the practices used before the Romans advanced urban drainage to the point of constructing underground sewers. The open sewers followed existing drainage pathways and often were directed along the center of roadways (Kirby and Laurson 1932). The sewers were primarily meant to convey urban stormwater runoff, but the inviting open channels also became receptacles of trash and kitchen wastes. If flows in the sewers were sufficient the wastes and accumulated garbage would be flushed through the system to the disposal location, otherwise the waste accumulated. To combat the nuisance conditions that were developing the open channels were covered. In Paris, the first covered sewer dates to 1370 when Hugues Aubriot constructed the Fosse de St. Opportune (Reid 1991). This sewer, known as the “beltway sewer,” discharged into the Seine River and acted as a collector for the sewers on one side of the Seine. The outfall of the sewer, near the Louvre, produced terrible odors that even offended Louis XII. The disposal of human feces gradually became an issue in Paris and London during the Middle Ages as populations expanded in the two cities. Waste disposal in Paris was unregulated for the most part until a decree in 1530 required property owners to construct cesspools in each new dwelling (Reid 1991, pg. 10). In general, each community and neighborhood had a selfish attitude toward urban drainage and municipal services. Citizens were willing to pay for sewers to drain only their neighborhood into the next. The negligent attitude perpetuated the urban drainage perspective of an unneeded community service held shortly after the fall of the Roman Empire. There were consistent maintenance problems in European covered sewers during the Middle Ages. A survey of covered sewers in Paris conducted during 1636 found all 24 clogged and in serious disrepair (Krupa 1991). These findings, however, led to little improvement since the nobility and ruling class did not concern themselves with the sewerage of the masses. An ordinance passed in 1721 stated that property owners must pay for the cleaning of the covered sewers beneath their building. This action only exacerbated the urban drainage problem because property owners interpreted the ordinance to mean they had the right to dump all their refuse and garbage into the sewer system if they were paying for it. In 1736 and 1755 additional Acts were passed to deter illegal dumping into the covered sewers, but these were relatively unheeded. In England one of the first public Acts that addressed the sewerage issue was passed in 1427 (Sidwick 1977). This Act, which was appointed by the Commissioners of Sewers, addressed the control of surface water sewers and channels. The Act was redrafted in 1531 and remained essentially in force until the passage of the Public Health Act in 1848. However, the passage of local Acts during this time frame usually superseded the national legislation. The Act of 1427 displayed the improving interest of the ruling class regarding sanitation issues, but unfortunately the enforcement of the Acts was difficult. Similar to the Parisian ordinance, King Henry VIII wrote an edict that made each household responsible for clearing the sewer passing by their dwelling (Gayman 1997). The King was also responsible for empowering the Commission of Sewers, originally made possible by the passage of previous Acts. However, no money was provided to pay its members until 1622 when it was decided that fines for non-compliance could be used to fund its activities. Therefore, although

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both the ruling class attitude and societal opinion of urban drainage issues improved slightly, the systems remained a neglected afterthought throughout the medieval period. Switching our focus to the American continents we see the perspective of urban drainage change to public works systems requiring careful planning, construction, and maintenance. In South America the Incas understood the value of urban drainage practices. One prime example is the drainage system constructed in Machu Picchu, the royal estate of the Inca ruler Pachacuti. Wright and Valencia Zegarra (2000) studied the ruins of the estate in detail and reported the characteristics of the drainage system from an engineering perspective. The drainage system of Machu Picchu capitalized on years of trial-and-error experience the Incas had with constructing drainage infrastructure in other cities. The care used during planning and constructing the drainage system as an integrated part of the city suggests the Incas placed a high value on urban drainage from a practical viewpoint. The first large-scale urban drainage systems in North America were constructed in New England cities during the colonial era (APWA 1976). Roadway drainage was vital to make the roads passable by horse-drawn carriages. Boston, Philadelphia, and New York constructed stone roadways with surface and subsurface drainage systems in the early eighteenth century. The roads in Boston were especially carefully constructed with a crown in the center and gutters along the sides. The first sewers were built of primarily wood, brick, and stone during the colonial era in commercial areas of the major New England cities (APWA 1976). Private wooden sewers were constructed in the late seventeenth century to drain cellars. In 1704, Bostonian Francis Thrasher was given permission to construct a sewer that would be “beneficial to the common citizen” (APWA 1976), marking one of the first common sewers legally constructed in New England. The city selectman subsequently ordered those who connected to the sewer to help pay for the project. The first underground sewer constructed in Boston during the early eighteenth century turned out to be extremely popular. Soon after the success of the project was known, numerous other sewer projects were initiated. From 1708 to 1736 a total of 654 sewer construction permits were issued in Boston for projects that required careful street replacement after completion (APWA 1976). The construction of sewers in Boston contributed to it being labeled as one of the “most dry and clean cities in the world.” Philadelphia was another major New England city that experienced significant sewer construction activities. Most sewers constructed in Philadelphia during the seventeenth century were made of wood. But, in 1700 Pennsylvania passed a law that required all subsurface sewers to be constructed of brick or stone, instead of wood (APWA 1976). Despite the efforts in sewer construction the city of Philadelphia continued to experience urban drainage problems because of the poor maintenance of the sewers. New sewers were quickly filled in with solid material and gradually became dilapidated. In general, the purpose of the sewers in colonial New England was primarily urban stormwater drainage, although waste removal was a consistent unplanned function. Urban drainage philosophy in colonial New England cities was very similar to European practices. Human feces were managed on-site in cesspools or privy vaults, while common sewers were constructed to

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drain urban stormwater runoff. Moreover, individuals were only willing to pay for common sewers to drain their own neighborhood if flooding and nuisance conditions were frequent. Development of Modern Urban Drainage Practices "The sophistication of a civilization can often be judged by its attention to the issue of drainage infrastructure,..." -Wright and Valencia Zegarra (2000) The beginning of modern urban drainage practices was initiated in European cities during the nineteenth century. The Paris sewer system was improved by the initial efforts of the engineer Pierre-Emmanuel Bruneseau (Reid 1991). Bruneseau documented the deterioration of the sewers by leading expeditions into the underground labyrinth. Bruneseau’s reports to the Emperor described the disastrous effects that the political upheaval had on the condition of the sewers. He argued for efforts to clean the sewers to demonstrate the superiority of the Empire compared to the preceding monarchy and revolutionary governments (Reid 1991). In addition, Bruneseau suggested that unhealthiness was among the major causes of depopulation. Despite Bruneseau’s efforts, his mission of reforming the Paris sewers was far from complete when he died in 1819. H.C. Emmery, head of the Paris sewer system from 1832 to 1839, furthered the development of the Paris sewers by replacing the open channels running along the center of streets with gutters constructed under sidewalks (Reid 1991). Inlets were provided from the gutters to the sewer system. During this time period and well into the nineteenth century the Paris sewers were all constructed large enough to allow a man to move about standing up. The Paris sewer system gained the reputation of being a refuge for criminals and undesirables during the first half of the nineteenth century. Hugo wrote of the Paris sewers during the nineteenth century in Les Misérables. Reid (1991) made the point that the subterranean sewer system’s relative relationship with the above ground city was symbolic of the class struggles during the time period. The sewer system was associated with the lower class, while the finer parts of Paris above ground were associated with the upper class. Many of the bourgeois of the period viewed the sewers as the origination of threats from disease (e.g., cholera) and social disorder (e.g., insurrection). This perception was supported during 1832 and again during 1849 with the outbreak of cholera and civil unrest, both of which impacted all classes. Burian et al. (1999) summarized the primary urban drainage developments in the United States during the nineteenth and twentieth centuries. The developments were grouped into nine categories: 1. Improvements in Pipe Materials, Construction Methods, and Maintenance Practices 2. Decision to Use Water-Carriage System of Waste Removal 3. Comprehensive Sewer-System Design 4. Combined- Versus Separate-Sewer Systems 5. Identification of Waterborne Diseases 6. Introduction of Wastewater Treatment 7. Advances in Urban Hydrology 8. Computer Advancements

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9. Environmental Awareness A comprehensive discussion of the historical developments within each of these categories is beyond the scope of this paper. However, the major changes in urban drainage perspectives during the time period can be summarized. One critical turning point in urban drainage occurred during the middle of the nineteenth century. During the first half of the nineteenth century sanitary wastes were discharged from buildings to privy vaults and cesspools. Most sewers were designed exclusively for stormwater drainage. Sanitary wastes accumulated in privy vaults and cesspools and were periodically collected by scavengers and transported to a suitable disposal location (e.g., farm, dump outside city). As the nineteenth century progressed the concept of urban drainage changed with the incorporation of water-carriage sanitary waste collection into the urban drainage systems. Sanitary connections to the sewers were made legal and new sewers were constructed to drain stormwater and sanitary wastewater. The public perspective of urban drainage changed during the nineteenth century from a neglected afterthought to a vital public works system. The public also shifted their stance regarding funding the construction and maintenance of sewer systems. The shift in public perspective was driven by many factors, but the most important was probably the scientific evidence accumulated during the second half of the century linking sanitary wastes and disease transmission. Municipal leaders, backed by strong public support, initiated massive projects to build comprehensive sewer systems in the larger cities in Europe and the United States. In 1843 Hamburg, Germany constructed the first comprehensively planned sewerage system for a major city (Metcalf and Eddy 1928). William Lindley was commissioned to plan and design the system after a fire destroyed a large part of the city during 1842. The success of the Hamburg sewer system led to the comprehensive design of sewer systems for other cities in Europe and the United States. The comprehensive sewer system of London, designed by Joseph Bazalgette, was constructed between 1859 and 1865 (Kirby and Laurson 1932). Figure 5 illustrates the magnitude of a major sewer construction project such as the London Main Drainage. In the United States during the 1850s, E. Sylvester Chesbrough designed the Chicago urban drainage system (Cain 1972) and Julius W. Adams designed a comprehensive system for Brooklyn (Adams 1880). George E. Waring, Jr. hastened the shift in public perspective of urban drainage in the United States during the second half of the nineteenth century from a neglected service to a vital public works system. Waring was outspoken about the economic and sanitary advantages of his version of the separate-sewer system (Waring 1873, 1875). Waring believed the anticontagionist theory of disease transmission and argued that his separate-sewer system could provide the rapid removal of wastes imperative to protect public health. His opinion swayed several city administrators to construct sewer systems. The perspective of urban drainage also changed from a design standpoint during the nineteenth century. Most sewers constructed before the nineteenth century were not planned or designed by an engineer using numerical calculations. Instead a trial-and-error process was executed, which in some cases eventually produced well functioning systems. During the nineteenth century the

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perspective of urban drainage design changed to incorporate the opinions of technical experts. The design of the Hamburg sewer system, for instance, incorporated engineering calculations. Empirical relationships were the first engineering calculations used. Most of the English speaking community was familiar with Roe’s Table (see Table 1) during the middle of the nineteenth century (Metcalf and Eddy 1928). Roe's Table, which indicated the catchment areas that could be drained by sewer of specified sizes laid at various slopes, was based on empirical observations of London sewers in the Holburn and Finsbury Divisions.

Figure 5. Photo of the construction of the Main Drainage of London during the 1860s (Walker 1987).

Table 1. Roe’s Table, showing the quantity of covered surface, from which circular sewers will convey away the water coming from a fall of rain of 1 inch in the hour, with house drainage, as ascertained in the Holburn and Finsbury Divisions (McMath 1887). Inclination Fall or Slope of Sewer Level ¼-in. in 10 feet ½-in. in 10 feet ¾-in. in 10 feet 1-in. in 10 feet 1 ½-in. in 10 feet 2-in. in 10 feet

2 Acres 39 43 50 63 78 90 115

2.5 Acres 67 75 87 113 143 165 182

3 Acres 120 135 155 203 257 295 318

Inner Diameter, or Bore, of Sewer in Feet 4 5 6 7 8 Acres Acres Acres Acres Acres 277 570 1020 1725 2850 308 630 1117 1925 3025 355 735 1318 2225 3500 460 950 1692 2875 4500 590 1200 2180 3700 5825 670 1385 2486 4225 6625 730 1500 2675 4550 7125

9 Acres 4125 4425 5100 6575 7850

10 Acres 5825 6250 7175 9250 11050

Other engineers developed their own design methods. Joseph Bazalgette calculated the volume of rainfall runoff that would be produced by a certain frequency event then estimated the limit of combined sewer overflows desired. From this information he determined the additional volume

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of pipe required for the system to function adequately. Buerger (1915) summarized sewer-sizing calculations available in the beginning of the nineteenth century and some of the more common empirical equations are shown below. Recall that most sewer systems constructed during the nineteenth century were combined; therefore, the formulas below were meant to size a single pipe to carry both dry weather wastewater and stormwater runoff. Hawksley (or Bazalgette): log d =

3 log A + log N + 6.8 10

where d = diameter of sewer (inches); N = length of sewer per foot of drop; and A = drainage area (acres).

Adams: q = CR 0.83

S 0.083 A 0.167

where q = discharge (cubic feet per second, cfs); C = an empirical coefficient; S = slope (feet per 1000 feet); A = drainage area (acres); and R = rainfall (inches per hour).

McMath: S 0.20 q = CR 0.20 A

During the second half of the nineteenth century the sewer design methods were significantly enhanced with the initial development of the present day Rational Method. Mulvaney (1851) in Ireland, Kuichling (1889) in the United States, and Lloyd-Davies (1906) in Great Britain all wrote on the practice of runoff computations and sewer pipe sizing and contributed concepts such as time of concentration that eventually evolved into the Rational Method. During the same time period that these engineers were developing the foundation of the Rational Method, the perspective of urban drainage was changing yet again. The focus of urban drainage shifted to include sewage treatment as water pollution and public health problems associated with unabated sewer discharges into receiving waters mounted. Treatment of urban drainage was limited in Europe and the United States during the early part of the twentieth century despite the scientific research demonstrating the linkage between sewage polluted waterways and disease transmission. By 1892, the United States had only 27 cities with wastewater treatment works (21 used land application and 6 used chemical precipitation) (Tarr 1979). The debate over wastewater treatment centered on whether it was more economical to treat the wastewater prior to discharge or treat the water source before distribution as potable water. At the turn of the century, most sanitary engineers agreed with the editorial stance taken by the Engineering Record in 1903:

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“… it is often more equitable to all concerned for an upper riparian city to discharge its sewage into a stream and a lower riparian city to filter the water of the same stream for a domestic supply, than for the former city to be forced to put in wastewater treatment works.”

Current Urban Drainage Perspectives Urban drainage in the early parts of the twentieth century was firmly established as a vital public works system. Engineers continued to improve design concepts and methods. During the second half of the twentieth century regulatory elements were promulgated in the United States, Europe, and other locations addressing urban drainage issues. Extensive monitoring efforts vastly improved the understanding of urban drainage quantity and quality characteristics (e.g., NURP in the United States). Computer modeling tools advanced the methods used to design and analyze urban drainage systems. Regulations, monitoring, computer modeling, and environmental concerns have altered the perspective of urban drainage from a public health and nuisance flooding concern during the first half of the twentieth century into a public health and nuisance flooding with additional concerns for ecosystem protection and urban sustainability. Methods to design and construct sustainable urban drainage systems are currently being researched and tested. Alternative development concepts (e.g., low-impact development) are influencing development practices to minimize the impacts of development on stormwater drainage. In addition, alternative on-site wastewater management strategies are being touted as more sustainable than centralized wastewater management for some situations. Communities are searching for innovative techniques to capture, detain, and use rainwater within the watershed instead of constructing massive drainage structures. Many communities are developing watershed-wide stormwater quality management plans to meet the dual objectives of flood prevention and water quality control. Urban drainage has indeed expanded significantly during the past few decades beyond a technical challenge to drain the urban area expeditiously to include the consideration of social, economic, political, environmental, and regulatory factors.

Summary In this paper we reviewed chronologically several urban drainage systems from 3000 BC to present. From this review three points stand out: •

The general public and city administrators viewed urban drainage systems as a convenient waste disposal system, an important flood control system, the cause or transmitter of disease, a vital system for the protection of public health, an underground refuge for criminals and undesirables, and a source of civic pride.



The purposes of urban drainage systems, including flood control, waste transport, water collection and recycling, often evolved through trial-and-error modifications after the systems were initially constructed.



Changes in perspective of urban drainage in one city were most often caused by disease outbreaks, scientific discoveries, or technical advances in planning, design, and construction.

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Before the nineteenth century, urban drainage was usually viewed as a vital natural resource, a convenient cleansing mechanism, an efficient waste transport medium, a flooding concern, a nuisance wastewater, or a transmitter of disease. During the nineteenth century urban drainage developments in Europe and United States modified the public perspective of urban drainage significantly. By the end of the nineteenth century urban drainage was viewed as a highly important public works system worthy of massive expenditures to prevent disease transmission. Currently, well-planned urban drainage is viewed as a vital component of a sustainable urban system.

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