Low Impact Development and Sustainable Stormwater Management in the 21 st Century. Thomas H. Cahill, P. E. Consultant Water Resources Engineering

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1 Low Impact Development and Sustainable Stormwater Management in the 21 st Century Thomas H. Cahill, P. E. Consultant Water Resources Engineering

2 We started trying to manage our stormwater runoff about 40 years ago.. Prior to that, we had spent a century building dams to capture and hold excess runoff

3 But our thinking has evolved, from managing or controlling runoff to building a better habitat. Low Impact Development

4 HABITAT it inhabits

5 HABITAT Since our species first walked upright across the East African Plain 4.5 Million years ago, we have sought two essential criteria for habitat shelter from the elements and each other a source of water fresh and constant

6 Olduvai Gorge, Tanzania

7 Olduvai Gorge, Rift Valley, Tanzania The Leakeys discovered the first evdience of humans (Lucy) and footprints in the rock dated 2.5 to 3.5 MY ago Since then, other excavations have yielded fossil bones dated 4 to 5 MY ago further north the Rift Valley, from deeper deposits

10 Human Development Genetic research suggests that all living humans (7 B) are descended from a common ancestor who lived in East Africa some 80,000 years ago

11 Humans first sought shelter in the Rift Valley Habitats were built with local vegetation STICKS and DIRT

13 Oldest Human Habitat Natural Stone Structures Southern France (Dordogne Valley) occupied 45,000 years ago Nearby caves (Lascaux) occupied 30,000 years ago Neanderthal cave dwellings dated from 60,000 years ago

15 Ice Age Some 2.5 MY ago the planet began a cycle of glaciation The planet was in the grip of the last period of glaciers until 25,000 years ago, when the planet warmed and the ice began to recede

19 By 15,000 years ago the ice was gone, replaced by woodlands, and occupied by humans, who had spread across the planet Where carbonate rocks lined valley walls along rivers, caves provided good habitat

20 Civilzation All that we think of as civilization began about 15,000 years ago The Fertile Cresent, stretching in an arc from what is now Iraq, through modern Turkey and down to the Mediterranean coast, contained the first clusters of habitats We lived together because it allowed a division of labors and security We built our habitats near water

21 Fertile Crescent Neolithic Revolution

22 Early Villages clusters of habitats Natufian settlements (15,000 Years ago) hunter-gathers (Paleolithic era) stacked stone huts animal hide roofs 18 to several hundred people Abandoned when it when the climate turned cold for 1,200 years (11,600 years ago) As it warmed again, farming began (10,000) Neolithic era

24 First Temple Gobekli Tepe, Turkey Quarried stone pillars, tilt-up construction Stone walls Unclear if the function was religious or recreational

25 First Temple - GOBEKLI TEPE

26 First City Catalhoyuk, Turkey (9,400 years ago) Domestication of animals (pigs, cattle) Thousands lived in linked, multi-room homes, interior walls were decorated with images and skulls of ancestors

27 CATALOYUK

28 Stone buildings Humans moved out of their caves and down the hill to build structures along the river valley, building with local stone, trees and clay

31 Stone villages For security, the best location for clustered habitats was at the top of the hill, But groundwater (spring) was critical

33 Tuscan hilltop village settled 3,000 years ago caves and springs at the hilltop Romans took over and added a new water supply system the aqueduct

35 The past two thousand years have followed this pattern of habitat building, from villages of vegetation to cities of brick and stone and although we had learned to bring the water to the habitats, we forgot how for a thousand years

38 and always build next to a river or made sure that wells were possible castles would catch the runoff from rooftops and store it in a cistern

48 Within the past century, we filled in the land between urban habitats with impervious surfaces

49 Impervious Surfaces The change began at the end of the 19 th Century, when the battle over what energy system would power the new automobile was settled GASOLINE vs. STEAM

51 Refinement of Oil for Gasoline became the new energy source Refining oil resulted in tar as a residual product, and was combined with MacAdam stone roads to produce AC

52 TARMAC (AC) soon covered every community between habitats and connected cities

53 The more we paved, the more we drove, the more we refined gasoline and produced more tar An endless cycle

54 In the 17 th and 18 th centuries we had developed piping systems of wood and cast iron and pumps to convey water to all habitats within the city

55 But it was the desire to bring water into our habitats that led to indoor plumbing We had common bath houses and latrines from roman times, but did not bathe or flush in our habitats

56 By the 18 th Century we were bathing on a regular basis and discharging our wastewater to the local street or stream

58 Although we had built common multi-occupant stone latrines two thousand years before, the water closet was developed by John Harrington in 1592 for Queen Elizabeth I, and then forgotten for a century

59 By the mid-1800 s, Thomas Crapper evolved a system of sewage conveyance that greatly increased the water demand of every habitat. From a few gallons to hundreds of gallons

building of STP s in the early 20 th century Paving over of the city

60 Combined Sewer System in Philadelphia Began with the enclosure of streams during the late 19 th century Realized the problem with the building of STP s in the early 20 th century Paving over of the city took place in the early 20 th century with the introduction of the automobile

61 Philadelphia Sewersheds More than half of Philadelphia is served by a combined sewer system. Source: Philadelphia Water Department

62 So we had sealed over the urban suface with pavements and built inlets to drain rainfall into the new sewer system, where it combined with sewerage

63 Within the urban environment, the residential communities did leave some green space and soil around most habitats Front and back yards

65 But we took the rainfall from every rooftop and conveyed it into the combined sewers No rain was allowed to soak into the remaining soil. By Ordinance

66 By the end of the 19 th Century, we also had added an additional requirement for the water supply to our habitats ENERGY

67 Downtown Pittsburgh

68 Vertical villages Needed energy to supply water to the top Habitats stacked on top of each other

70 HABITAT 20 th Century Security Water Energy

71 As the 20 th Century evolved, our cities began to grow beyond their boundaries The beginning of SUBURBIA

73 And we continued to pave over the soil with impervious materials. And conveyed the rain into local surface waters

79 IMPERVIOUS SURFACES In new suburban development, the amount of impervious surfaces for people is 25%, and for autos it is 75% In older dense urban development, the ratio is closer to 60% - 40%

80 By the 1960 s, the issue of stormwater runoff had become a serious problem, in both urban and suburban environments

81 STORMWATER carries a tremendous load of pollution Sediment, nutrients (Phosphorus and Nitrogen), heavy metals, organic compounds (both natural and manmade), bacteria, pesticides and herbicides

83 Non-point source pollution

85 DETENTION BASINS proposed by the SCS in the late 1960 s Designed to mitigate the rate of runoff from development Hold and release the runoff after a few hours Do not SIGNIFICANTLY reduce the VOLUME of runoff

88 New Development Detention Basins

91 Annual Hydrologic Cycle For an Average Year

92 Altered Hydrologic Cycle

93 Effects of Urbanization Reduces Infiltration Diminished flow during dry periods Increases Direct Runoff Flash flooding & Streambank erosion Increases Pollutants Degraded water quality

94 Stormwater Management acronyms (1960 s) NPS pollution was the initial focus (1970 s) BMPs were selected to solve the problem (1990 s) LID became a descriptive term for both structural and non-structural measures ( by 2020) Living buildings- zero net increase in water and energy

95 Stormwater Management in the 21 st Century VOLUME REDUCTION WATER QUALITY RATE CONTROL

96 New Development and Redevelopment The same methods and materials apply to both types of design In the built environment, we frequently have a sewer system in place that combines stormwater with sewage (CSOs) LID reduces the stormwater inflow to CSOs (1 or less) For Separate Storm Sewer Systems (MS4) the same design solutions work, but design criteria are more stringent (2.5 )

97 ANNUAL RAINFALL Atlanta, GA 50 West Chester, PA 45 Pittsburgh, PA 38 Chicago, IL 36 Austin, TX 34 Los Angeles, CA 15 San Diego, CA 10 Las Vegas, NV 4

98 Rainfall Distribution by Storm Size in Pasadena, CA: (Average Rainfall = 20.4"/yr) <1" 39% 5"+ 4% 4" - 5" 5% 3" - 4" 7% 2" - 3" 15% 1" - 2" 30%

99 2-year Frequency Rainfall (in 24 hours) (Comprises 95% of the Annual Rainfall) West Chester, PA 3.3 Seattle, WA 3.2 Chapel Hill, NC 3.6 Los Angeles, CA 2.9 Minneapolis, MN 2.5

100 VOLUME REDUCTION USES 3 METHODS; INFILTRATION EVAPO-TRANSPIRATION CAPTURE/REUSE 100

101 STORMWATER is a lost resource

102 Rainfall is for drinking On many parts of the planet, people capture and drink the rain that falls on their rooftops (New Zealand)

103

Climate Smart Communities Green Infrastructure Case Studies

New York State Water Resources Institute Climate Smart Communities Green Infrastructure Case Studies Emily Vail Hudson River Estuary Program NYS Department of Environmental Conservation Cornell University