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Swale drawings

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Doug Crouch
Doug Crouch

The document provides information on calculating the catchment area, runoff volume, and water holding capacity of swales for different surfaces. It gives the catchment area and runoff calculations for examples like a Walmart parking lot and corn/soybean fields in Iowa. It also lists Brad Lancaster's 7 principles of rainwater harvesting with earthworks which focus on observing water flows, starting at high points, slowing and spreading water, planning overflow routes, using living groundcover, and getting strategies to serve multiple functions through reassessment.

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Find the catchment area length ft x width ft= catchment area ft2 length m x width m= catchment area m2 60 ft 18.3 m 57 ft 17.4 m 46 ft 14 m 22 ft 6.7 m
60 ft 18.3 m 22 ft 6.7 m 60 ft x 22 ft= 1320 ft2 18.3 m x 6.7 m= 122.6 m2 Find the catchment area
35 ft 10.7 m 46 ft 14 m 35 ft x 46 ft= 1610 ft2 10.7 m x 14 m= 149.8 m2 Find the catchment area
60 ft 18.3 m 57 ft 17.4 m 46 ft 14 m 22 ft 6.7 m 1320 ft2 + 1610 ft2 = 2930 ft2 122.6 m2 + 149.8 m2 = 272.4 m2 Find the catchment area
Possible Volume from Runoff Catchment area ft2 x rainfall ft x 7.48 gal/ft3 = maximum runoff in gal Catchment area m2 x rainfall mm = maximum runoff in liters
Volume from Runoff 1320 ft2 x 3.58 ft x 7.48 gal/ft3= 35347.49 gal 122.6 m2 x 1092 mm= 133879.2 l Possible Volume from Runoff Catchment area ft2 x rainfall ft x 7.48 gal/ft3 = maximum runoff in gal Catchment area m2 x rainfall mm = maximum runoff in liters Avg. rainfall in Cincinnati = 43 in 43 in- = 3.58 ft 43 in = 1.092 m 1 ft = .3048 m 22 ft 6.7 m catchment area 60 ft x 22 ft= 1320 ft2 18.3 m x 6.7 m= 122.6 m2 60 ft 18.3 m
Volume from Runoff 35 ft 10.7 m 46 ft 14 m catchment area 35 ft x 46 ft= 1610 ft2 10.7 m x 14 m= 149.8 m2 1610 ft2 x 3.58 ft x 7.48 gal/ft3= 43113.2 gal 149.8 m2 x 1092 mm= 163581.6 L
60 ft 18.3 m 57 ft 17.4 m 46 ft 14 m 22 ft 6.7 m catchment area 1320 ft2 + 1610 ft2 = 2930 ft2 122.6 m2 + 149.8 m2 = 272.4 m2 Volume from Runoff 35347.49 gal + 43113.2 gal = 78460.7 gal 133879.2 l + 163581.6 l= 297460.8 l
Estimated Net Runoff from a Catchment Surface Adjusted by its Runoff Coefficient catchment area (ft2) x rainfall (ft) x 7.48 gal/ft x runoff coefficient = net runoff (gal) 60 ft 18.3 m 57 ft 17.4 m 46 ft 14 m 22 ft 6.7 m 297460.8 l x .9 = 267714.7 l Sample runoff coefficient Metal roofs lose 5% thus coefficient 95% Concrete & Asphalt 90% Built up tar and gravel roofs 80-85% Clay tile roof?? 78460.7 gal x .9= 70614.63 gal
60 ft 18 m 22 ft 6.6 m 35 ft 10.5 m 46 ft 13.8 m 60 ft 18 m 57 ft 17.1 m 46 ft 13.8 m 22 ft 6.6 m
3-5 ft or 1-1.5 m 1-3 ft or .3- 1 m
Calculating water holding capacity of the swale Area = ½ x width x depth (formula for a triangle) Volume of Water Holding Capacity= Area x length Volume = ½ x width x depth x length width-= 5 ft or 1.5 m Depth = 3 ft or .9 m Length= 90 ft or 30 m
Calculating water holding capacity of the swale Volume = ½ x width x depth x length .5 x 5ft x 3ft x 90ft = 675 ft3 675 ft 3 x 7.48 gal/ft3 = 5,049 gal .5 x 1.5m x .9m x 30m = 20.25 m3 20.25 m3 x 1,000 liters/m= 20,250 l width-= 5 ft or 1.5 m Depth = 3 ft or .9 m
Estimated Net Runoff from a Catchment Surface Adjusted by its Runoff Coefficient catchment area (ft2) x rainfall (ft) x 7.48 gal/ft x runoff coefficient = net runoff (gal) 60 ft 18 m 57 ft 17.1 m 46 ft 13.8 m 22 ft 6.6 m
Estimated Net Runoff from a Catchment Surface Adjusted by its Runoff Coefficient catchment area (ft2) x rainfall (ft) x 7.48 gal/ft x runoff coefficient = net runoff (gal) 60 ft 18 m 57 ft 17.1 m 46 ft 13.8 m 22 ft 6.6 m Volume from Runoff 1320 ft2 x .083 ft x 7.48 gal/ft3= 819.5 gal 1610 ft2 x .083 ft x 7.48 gal/ft3= 999.55 gal Total=1819.05 gal
 
Walmart parking Lot -17 acres Runoff?
Walmart parking Lot -17 acres Runoff=16,370,116 x .083 ft x 7.48=10,163,222.8 gal
Corn and Soy-23,500,000 acres State of Iowa- 35,922,000 acres Runoff=168,885,558,744 x .083 ft x 7.48=126,323,979,405 gal
Corn and Soy-23,500,000 acres State of Iowa- 35,922,000 acres Runoff=168,885,558,744 x .083 ft x 7.48=104,850,910,290 gal X .65=68,153,091,688 104,850,910,290 gal X .2=136,306,183,377 136,306,183,377-68,153,091,688=68153091689 gal
Brad Lancaster’s Principles of Rain water harvesting with Earthworks 1. Begin with long and thoughtful observation.
Use all your senses to see where the water flows and how. What is working, what is not? Build on what works .2. Start at the top (highpoint) of your watershed and work your way down.
Water travels downhill, so collect water at your high points for more immediate infiltration and easy gravity-fed distribution. Start at the top where there is less volume and velocity of water. 3. Start small and simple. 
Work at the human scale so you can build and repair everything. Many small strategies are far more effective than one big one when you are trying to infiltrate water into the soil .4. Slow, spread, and infiltrate the flow of water. 
Rather than having water run erosively off the land’s surface, encourage it to stick around, “walk” around, and infiltrate into the soil. Slow it, spread it, sink it .5. Always plan an overflow route, and manage that overflow as a resource.
Always have an overflow route for the water in times of extra heavy rains, and where possible, use the overflow as a resource .6. Maximize living and organic groundcover.
Create a living sponge so the harvested water is used to create more resources, while the soil’s ability to infiltrate and hold water steadily improves.

7. Maximize beneficial relationships and efficiency by “stacking functions.”
Get your water harvesting strategies to do more than hold water. Berms can double as high-and-dry raised paths. Plantings can be placed to cool buildings in summer. Vegetation can be selected to provide food.

8. Continually reassess your system: the “feedback loop.”
Observe how your work affects the site, beginning again with the first principle. Make any needed changes, using the principles to guide you.

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Swale drawings

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  • 10. Find the catchment area length ft x width ft= catchment area ft2 length m x width m= catchment area m2 60 ft 18.3 m 57 ft 17.4 m 46 ft 14 m 22 ft 6.7 m
  • 11. 60 ft 18.3 m 22 ft 6.7 m 60 ft x 22 ft= 1320 ft2 18.3 m x 6.7 m= 122.6 m2 Find the catchment area
  • 12. 35 ft 10.7 m 46 ft 14 m 35 ft x 46 ft= 1610 ft2 10.7 m x 14 m= 149.8 m2 Find the catchment area
  • 13. 60 ft 18.3 m 57 ft 17.4 m 46 ft 14 m 22 ft 6.7 m 1320 ft2 + 1610 ft2 = 2930 ft2 122.6 m2 + 149.8 m2 = 272.4 m2 Find the catchment area
  • 14. Possible Volume from Runoff Catchment area ft2 x rainfall ft x 7.48 gal/ft3 = maximum runoff in gal Catchment area m2 x rainfall mm = maximum runoff in liters
  • 15. Volume from Runoff 1320 ft2 x 3.58 ft x 7.48 gal/ft3= 35347.49 gal 122.6 m2 x 1092 mm= 133879.2 l Possible Volume from Runoff Catchment area ft2 x rainfall ft x 7.48 gal/ft3 = maximum runoff in gal Catchment area m2 x rainfall mm = maximum runoff in liters Avg. rainfall in Cincinnati = 43 in 43 in- = 3.58 ft 43 in = 1.092 m 1 ft = .3048 m 22 ft 6.7 m catchment area 60 ft x 22 ft= 1320 ft2 18.3 m x 6.7 m= 122.6 m2 60 ft 18.3 m
  • 16. Volume from Runoff 35 ft 10.7 m 46 ft 14 m catchment area 35 ft x 46 ft= 1610 ft2 10.7 m x 14 m= 149.8 m2 1610 ft2 x 3.58 ft x 7.48 gal/ft3= 43113.2 gal 149.8 m2 x 1092 mm= 163581.6 L
  • 17. 60 ft 18.3 m 57 ft 17.4 m 46 ft 14 m 22 ft 6.7 m catchment area 1320 ft2 + 1610 ft2 = 2930 ft2 122.6 m2 + 149.8 m2 = 272.4 m2 Volume from Runoff 35347.49 gal + 43113.2 gal = 78460.7 gal 133879.2 l + 163581.6 l= 297460.8 l
  • 18. Estimated Net Runoff from a Catchment Surface Adjusted by its Runoff Coefficient catchment area (ft2) x rainfall (ft) x 7.48 gal/ft x runoff coefficient = net runoff (gal) 60 ft 18.3 m 57 ft 17.4 m 46 ft 14 m 22 ft 6.7 m 297460.8 l x .9 = 267714.7 l Sample runoff coefficient Metal roofs lose 5% thus coefficient 95% Concrete & Asphalt 90% Built up tar and gravel roofs 80-85% Clay tile roof?? 78460.7 gal x .9= 70614.63 gal
  • 19. 60 ft 18 m 22 ft 6.6 m 35 ft 10.5 m 46 ft 13.8 m 60 ft 18 m 57 ft 17.1 m 46 ft 13.8 m 22 ft 6.6 m
  • 20. 3-5 ft or 1-1.5 m 1-3 ft or .3- 1 m
  • 21. Calculating water holding capacity of the swale Area = ½ x width x depth (formula for a triangle) Volume of Water Holding Capacity= Area x length Volume = ½ x width x depth x length width-= 5 ft or 1.5 m Depth = 3 ft or .9 m Length= 90 ft or 30 m
  • 22. Calculating water holding capacity of the swale Volume = ½ x width x depth x length .5 x 5ft x 3ft x 90ft = 675 ft3 675 ft 3 x 7.48 gal/ft3 = 5,049 gal .5 x 1.5m x .9m x 30m = 20.25 m3 20.25 m3 x 1,000 liters/m= 20,250 l width-= 5 ft or 1.5 m Depth = 3 ft or .9 m
  • 23. Estimated Net Runoff from a Catchment Surface Adjusted by its Runoff Coefficient catchment area (ft2) x rainfall (ft) x 7.48 gal/ft x runoff coefficient = net runoff (gal) 60 ft 18 m 57 ft 17.1 m 46 ft 13.8 m 22 ft 6.6 m
  • 24. Estimated Net Runoff from a Catchment Surface Adjusted by its Runoff Coefficient catchment area (ft2) x rainfall (ft) x 7.48 gal/ft x runoff coefficient = net runoff (gal) 60 ft 18 m 57 ft 17.1 m 46 ft 13.8 m 22 ft 6.6 m Volume from Runoff 1320 ft2 x .083 ft x 7.48 gal/ft3= 819.5 gal 1610 ft2 x .083 ft x 7.48 gal/ft3= 999.55 gal Total=1819.05 gal
  • 25.  
  • 26. Walmart parking Lot -17 acres Runoff?
  • 27. Walmart parking Lot -17 acres Runoff=16,370,116 x .083 ft x 7.48=10,163,222.8 gal
  • 28. Corn and Soy-23,500,000 acres State of Iowa- 35,922,000 acres Runoff=168,885,558,744 x .083 ft x 7.48=126,323,979,405 gal
  • 29. Corn and Soy-23,500,000 acres State of Iowa- 35,922,000 acres Runoff=168,885,558,744 x .083 ft x 7.48=104,850,910,290 gal X .65=68,153,091,688 104,850,910,290 gal X .2=136,306,183,377 136,306,183,377-68,153,091,688=68153091689 gal
  • 30. Brad Lancaster’s Principles of Rain water harvesting with Earthworks 1. Begin with long and thoughtful observation.
Use all your senses to see where the water flows and how. What is working, what is not? Build on what works .2. Start at the top (highpoint) of your watershed and work your way down.
Water travels downhill, so collect water at your high points for more immediate infiltration and easy gravity-fed distribution. Start at the top where there is less volume and velocity of water. 3. Start small and simple. 
Work at the human scale so you can build and repair everything. Many small strategies are far more effective than one big one when you are trying to infiltrate water into the soil .4. Slow, spread, and infiltrate the flow of water. 
Rather than having water run erosively off the land’s surface, encourage it to stick around, “walk” around, and infiltrate into the soil. Slow it, spread it, sink it .5. Always plan an overflow route, and manage that overflow as a resource.
Always have an overflow route for the water in times of extra heavy rains, and where possible, use the overflow as a resource .6. Maximize living and organic groundcover.
Create a living sponge so the harvested water is used to create more resources, while the soil’s ability to infiltrate and hold water steadily improves.

7. Maximize beneficial relationships and efficiency by “stacking functions.”
Get your water harvesting strategies to do more than hold water. Berms can double as high-and-dry raised paths. Plantings can be placed to cool buildings in summer. Vegetation can be selected to provide food.

8. Continually reassess your system: the “feedback loop.”
Observe how your work affects the site, beginning again with the first principle. Make any needed changes, using the principles to guide you.