Artful Rainwater Design

Creative Ways to Manage Stormwater

Stuart Echols, Eliza Pennypacker

• Publisher: Island Press
• Year: 2015
• Print ISBN: 9781610912662, 9781610910514
• eBook ISBN: 9781610913188
• Topic: Architecture
• Subtopic: Architecture General

Stormwater management as art? Absolutely. Rain is a resource that should be valued and celebrated, not merely treated as an urban design problem—and yet, traditional stormwater treatment methods often range from ugly to forgettable. Artful Rainwater Design shows that it's possible to effectively manage runoff while also creating inviting, attractive landscapes.
 
This beautifully illustrated, comprehensive guide explains how to design creative, yet practical, landscapes that treat on-site stormwater management as an opportunity to enhance site design. Artful Rainwater Design has three main parts: first, the book outlines five amenity-focused goals that might be highlighted in a project: education, recreation, safety, public relations, and aesthetic appeal. Next, it focuses on techniques for ecologically sustainable stormwater management that complement the amenity goals. Finally, it features diverse case studies that show how designers around the country are implementing principles of artful rainwater design.
 
Artful Rainwater Design is a must-have resource for landscape architects, urban designers, civil engineers, and architects who won't let stormwater regulations cramp their style, and who understand that for a design to truly be sustainable, people must appreciate and love it. It is a tool for creating landscapes that celebrate rain for the life-giving resource it is—and contribute to more sustainable, healthy, and even fun, built environments.

1. The History of Stormwater Management and Background for Artful Rainwater Design

Although rainwater has been considered a resource in agricultural contexts for millennia, in urban contexts it has historically been considered a waste product. With some exceptions in historical management strategies, urban rainwater was treated as a problem to be mitigated, a waste product to be eliminated or controlled.

However, recent innovations in stormwater management have catalyzed a transition from treating urban runoff as undesirable to appreciating it as a natural resource that must be managed with great care. Management strategies have shifted in past decades, from simple flood control levees and combined storm and sewer systems to onsite detention systems intended to control excess flow rates, and later to infiltration and rainwater harvesting systems intended to reduce runoff volumes and non–point source pollution. Since the 1990s there has been greater interest in treating rainwater as a resource for groundwater and surface water recharge, especially through infiltration and biofiltration. In the late 1990s, authors of some regulations and publications began to call for stormwater management to include the goal of creating amenity in addition to reducing runoff quantity and quality. And since the early 2000s, some designers have begun to effectively address all three goals and celebrate rainwater through the creation of Artful Rainwater Designs (ARDs). This part presents background understanding of this transition in stormwater management and how it has evolved into ARD.

ADDRESSING STORMWATER RUNOFF QUANTITY: TRADITIONAL FLOOD MANAGEMENT

For thousands of years, stormwater management focused exclusively on flood prevention. Even in 1760 b.c.e., King Hammurabi of Mesopotamia presented stormwater regulations in the Code of Hammurabi to protect downstream landowners:

Figure 1.1. Historically, stormwater management focused on flood control; the design of systems like this detention basin considered neither beauty nor even visibility, because they were often located out of the public eye (design: unknown; photograph: Stuart Echols).

Figure 1.2. Over time, designers began to realize that stormwater management systems could also provide habitat and amenity, as in the case of this wet detention pond (design: unknown; photograph: Stuart Echols).

Figure 1.3. Today, designers see benefit in locating sustainable stormwater management systems in highly visible spots, making them beautiful, and providing means for the public to learn how the system works, as at this rainwater biotope at the Visitor Center entrance in the Queens Botanical Garden (design: Atelier Dreiseitl and Conservation Forum, BKSK Architects; photograph: Stuart Echols).

Section 53. If anyone be too lazy to keep his dam in proper condition, and does not keep it so; if then the dam breaks and all the fields are flooded, then shall he in whose dam the break occurred be sold for money and the money shall replace the crop which he has caused to be ruined.

Section 55. If anyone open his ditches to water his crop, but is careless, and the water floods the field of his neighbor, than he shall repay his neighbor with crop for his loss.

Section 56. If a man lets out the water, and the water overflows the land of his neighbor, he shall pay 10 gur of crop for every 10 gan of land flooded.¹

Controlling the quantity of water was the exclusive goal. From earliest times the emphasis was on protecting property from flood damage by moving the water offsite; more recently, the focus expanded to protection of natural water bodies from the impact of erosion caused by flooding. In both, the basic strategies were conveyance and detention.

Flood Management Tools: Basins, Channels, and Pipes

As stated earlier, the historic underpinning of urban stormwater management was the simple desire to convey runoff away from structures and protect local property from flooding. As Roesner and Matthews, whose engineering firm specialized in “integrated solutions in water,” explained in their often-cited article “Water Management in the 1990s,”

Historically, stormwater management has been limited to planning, designing and implementing storm drainage improvements. For the most part, planning and design have focused on protecting only the site being drained, with little consideration of the downstream effects of resulting increases in volume and peak flows.²

But the inherent problem with this focus on localized flooding, as Roesner and Mathews explained, was that flooding impacts on the downstream natural drainage system were literally out of sight and out of mind.

Stormwater flood management by conveyance was historically achieved by drainage systems that would quickly move a storm’s peak flow downstream (consider, for example, the array of combined sewer conveyance tunnels in ancient Rome that disgorged from the mighty Cloaca Maxima into the Tiber River). The primary focus on managing stormwater was to dispose of the water as quickly as possible; there was no concern for preservation of stream flow rate, volume, frequency, duration, or water quality; management techniques focused simply on safely moving water away. For millennia, this entailed sizing pipes and drainage ways large enough to efficiently move the water away from a site. The common convention was to look at the size of a pipe in a comparable drainage situation and replicate that size in the hope that it would be adequate. This worked well enough if the pipe was, for example, conveying stormwater under a rural road, but once piped sewer systems were developed to handle urban runoff, the possibility of overflow from inadequately sized pipes became a real danger.

The first effective method to estimate flood flow was developed by Irish engineer Thomas Mulvaney in 1851 and made popular in the United States by Emil Kuichling. Mulvaney assumed rainfall was naturally disposed of in three ways: evaporation, infiltration, and runoff. He reasoned that evaporation and infiltration were constant throughout the year and that only daily runoff would vary with rainfall amounts. As a result, the “rational method” of runoff calculation was developed to focus specifically on predicting peak runoff flow rates resulting from the largest storm in a completely impervious urban situation. The rational method gave designers a means to predict stormwater runoff in urban areas so that pipes could be sized to dispose of the water and thus prevent local flooding. This method proved so simple that it is still used today to calculate surface water flow. But one of the inherent problems in this approach is that it ignores evapotranspiration and infiltration as useful stormwater management strategies.

Another problem with the historical approach to piping stormwater offsite lay in the fact that as these peak flows were successfully conveyed away, downstream land was still subject to increased flooding (Strom & Nathan, 1993, p. 87). In all of these approaches, stormwater in the urban environment was seen not as a resource but as a forceful enemy. According to Tourbier, a pioneer in sustainable landscapes and author of Best Management Practices for Stormwater,

Stormwater management had its origin in what was known in legal language as the common enemy rule: draining runoff away from houses and backyards as fast as possible. As populations grew, this practice proved to be detrimental because one person’s backyard drained into someone else’s front yard. The runoff then accumulated, resulting in flood damage downstream. For many years the [United States] federal government was heavily involved in flood control, only to discover an ever-increasing spiral of expenditures, but still mounting flood losses.³

As if flooding weren’t problem enough, stormwater too often caused even more damage when combined with sewage. Since ancient times, pipes in cities often carried both stormwater and sewage. Rome’s Cloaca Maxima, mentioned earlier, remains a famous example, an engineering marvel that discharged not only rain runoff but also sewage directly into the Tiber River. Despite resulting quality degradation of rivers and other surface waters on the receiving end of combined sewer systems (CSSs), for centuries they were considered an efficient means of discarding unwanted urban liquids, and in fact CSSs were seen as a clever way to use stormwater both to move and to dilute sewage. Cities everywhere, including those in the United States, commonly built CSSs as late as the early twentieth century. But what happens when large rain events flood CSS pipes? At worst (and far too often) they fill and backflow, sending sewage backwards to its original source or simply letting the sewage overflow into streams, rivers, lakes, sounds, and bays. This unfortunate occurrence is known today as a combined sewer overflow (CSO), and it is a problem that cities worldwide seek to prevent. Most cities stopped building CSSs, but many still struggle with CSOs in their older piping systems. In sum, managing stormwater by piping it offsite arguably created more problems than it solved.

Note that Section 53 of Hammurabi’s code demanded maintenance of dams, which raises the subject of detaining stormwater on site, another historical management strategy to prevent runoff from resulting in flooding. The detention basin is simple in concept. First, create a basin into which stormwater runoff is directed. Second, ensure that water is released slowly enough from the basin that local downstream damage from flooding is prevented. Much like a bathtub, detention basins must be large enough to store the volume of water resulting from a large storm, and, like the bathtub drain, an outlet is sized to control the peak flow rate of the water released from the basin. Although codes to this day state that detention must control postdevelopment peak water discharge at a predevelopment rate, downstream problems still occur because of two errors in reasoning. First, stormwater detention methods fail to recognize that when water is simultaneously released from a large number of basins, each at the maximum legal flow rate, these flows combine downstream and cause flooding once again. But because this flooding is caused by legal basin drainage and occurs so far downstream, it’s hard to blame a specific landowner for the cause.

The second error is the assumption that release of water from detention basins has no negative impact on stream channels: Because water flows from each basin at predevelopment rates, streams should be fine. Once again we see a failure to recognize the cumulative impact of discharge from many detention basins simultaneously. The result is that natural streams endure bankfull (i.e., “to the brim”) flows for unnaturally long periods of time, leading to scouring and stream bank erosion. Solutions to this problem were not addressed until the 1980s, when issues of stream bank erosion from detention basin discharge were more fully recognized.

In sum, traditional stormwater management practices generally addressed only excess runoff as a hazard to be contained, conveyed, and discarded as an unwanted byproduct of land development. Historical stormwater flood management practices were developed to control local urban flooding and protect local property, and they were never intended to emulate natural evapotranspiration, infiltration, and runoff processes. As a result, far from emulating natural hydrologic processes, these traditional management methods further destroyed healthy ecosystems, because the true environmental problem created by urban development was excess runoff volume created from reduced infiltration and evaporation. Treating rain as a waste product in some ways resulted in more problems than it solved.

The Detention Basin Saga Continues: Stream Channel Protection from Detention Basin Discharge

As stated earlier, for centuries detention basins managed local stormwater flooding but caused unintended downstream impacts.

Things changed with the release of Technical Release 20 by the Soil Conservation Service (TR-20) in 1982, which provided a particularly useful means to compute the stormwater runoff rate and volume for an entire watershed, effectively combining the downstream impacts of runoff from many sites. The TR-20 allowed improved modeling of the downstream flow levels and frequencies, including the downstream impacts of bankfull flows. This modeling program made it much easier to evaluate the combined effects of detention facilities located throughout a watershed and gave designers a better understanding of how these facilities affect flow rates at specific points in system. As a result, the location, size, and design of detention systems could be adjusted to release runoff at a much slower rate and thus reduce the downstream bankfull flows. This required regional stormwater planning and design. More importantly, it also required implementation on a regional scale, which seldom occurred before SCS-TR-20. The most common local stormwater facilities, however, remained on site detention, as required by most local land development regulations. This simple approach was, and still is, the easiest and most common.

A DIFFERENT TACK: ADDRESSING STORMWATER QUALITY

By the mid-twentieth century, regulators and researchers in the United States recognized that flooding wasn’t the only problem caused by stormwater moving downstream. Unfortunately, water also picks up pollutants in its path, so water bodies downstream can be polluted by stormwater carrying a wide range of toxins, from animal feces to hydrocarbons. And so quality joined quantity as a stormwater issue to be managed. Early strategies included a range of filtration methods, and by the 1980s and 1990s, biofiltration and infiltration began to be recognized as useful tools, which in turn led to promotion of green infrastructure as a strategy to effectively manage stormwater.

The Prelude: Point Source Pollution

As early as 1948, the US federal government decided to address the diminishing quality of the country’s lakes, rivers, and streams; every one should be swimmable and fishable, they reasoned. The Federal Water Pollution Control Act of 1948 mandated that states identify water bodies polluted beyond a “tolerable” level and that they locate and suppress the polluting discharge. Because of the difficulty of eliminating point sources of pollution, this act was not well enforced. According to Andrew Dzurik, emeritus professor of environmental engineering at Florida State University,

As a result of the inefficiency of such procedures, rivers were being turned into open sewers, the aquatic life of the Great Lakes was threatened with extinction, and the purity of water used for drinking, irrigation, and industrial uses was endangered.⁴

It wasn’t until the 1960s, considered a watershed moment in environmental awareness in the United States, that a set of significant demands regarding prevention of water pollution were introduced.

F...

Table of contents

• Cover
• About Island Press
• Title Page
• Copyright
• Contents
• Acknowledgments
• Introduction
• Part 1: The History of Stormwater Management and Background for Artful Rainwater Design
• Part 2: Achieving Amenity with Artful Rainwater Design
• Part 3: Achieving Utility with Artful Rainwater Design
• Part 4: Case Studies of Artful Rainwater Design
• Conclusion: Some Parting Thoughts
• Artful Rainwater Design Project List
• References
• Island Press | Board of Directors