Rethinking the design of infiltration facilities MSc Thesis presentation: Rethinking the design of...
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MSc Thesis presentation:
Rethinking the design of Rethinking the design of infiltration facilitiesinfiltration facilities
Leon Valkenburg
MSc thesis presentation Leon Valkenburg
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Welcome!
Introducing my committee:• Prof.dr.ir. Nick van de Giesen• Dr.ir. Frans van de Ven• Ir. Marie-Claire ten Veldhuis• Ir. Emil Hartman (DHV)
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Outline
1. Urban drainage problems2. Storm water infiltration3. The design4. Studying infiltration facilities5. Improving the design6. Conclusions and recommendations
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Problem 1: Pluvial flooding (wateroverlast)
Urban drainage problems
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Problem 2: Sewage spills (riooloverstorten)
Urban drainage problems
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Rain
Water goes to sewer
Urban drainage problems
Solution?
Storm water infiltration
Too much water: flooding
Unsaturated zone
Groundwater
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Storm water infiltrationSummarising infiltration facilities
Goal:• Keep the runoff close to its source• Reduce the load on the sewer system
Method:• Capture the rain from roofs and roads• Store and infiltrate it into the soil
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Storm water infiltration
Surface facility Subsurface facility
Combined facility
Types of infiltration facilities
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Storm water infiltrationInfiltration depends on:
• Soil type• Water level in facility• Groundwater level• Rainfall history• Temperature• Clogging rate
Animation
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The designHow big should the facility be?
Calculate storage and dimensions with:• In = design rainfall:
How much water is coming in?• Out = infiltration capacity:
How much water is going out?
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The designCurrent design practice
• Design rainfall: depth-duration-frequency curves• Infiltration capacity: use Darcy’s law
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The designCurrent design method is flawed:• Limitations design rainfall • Calculation of the outflow is not correct• Assumptions with a weak basis• Clogging can affect outflow
We don’t know how much water is going out!
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Studying infiltration facilities Why?• Infiltration capacity in practice is unclear• Improve the flawed design method
How?• Modelling in computer model• Measurements in facilities in practice
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Studying infiltration facilitiesModelling:• Use the computer model Hydrus• Find out how much water is going out in theory
Test performance infiltration facilities on:• Soil type• Groundwater level• Shape of facility• Temperature• Clogged bottom
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Influence groundwater level
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-0.5 0 0.5 1 1.5 2Depth groundwater level below bottom [m]
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Darcy dynamic
Darcy constant
Hydrus
Hydrus no GWL
Studying infiltration facilitiesModelling
What can you do with the results?• Find “the out” in various circumstances• Test the current design model
Comparing Hydrus with design method
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0.0 0.5 1.0 1.5 2.0 2.5 3.0Time [d]
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Darcy dynamic
Darcy constant
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Studying infiltration facilitiesMeasurements in facilities in practice
First step:• 90 Dutch municipalities (gemeenten) contacted• 23 responded• 4 had done monitoring (no suitable
measurements)
Result do measurements for this research
Municipality of Ede supported the measuring campaign
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Studying infiltration facilitiesThe location of Ede
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Studying infiltration facilitiesMeasurements in Ede
Two facilities tested:1. A soakaway from 19802. An infiltration unit from 2001
Test the performance by measuring:• Water level in facility• Soil moisture content: amount of water in the soil
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Studying infiltration facilitiesMeasurement setup
• Fill with tank truck
• Measure water level with diver
• Measure soil moisture with sensors
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Studying infiltration facilitiesPhoto impression
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Studying infiltration facilitiesMeasurement results
Soakaway:• Bottom is not
clogged• Functioned well
Infiltration unit:• Tested 2 times• Proved to be bigger• Infiltration unit could
not be filled• Functioned well
Soil moisture measurements
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0.0 5.0 10.0 15.0 20.0Time [h]
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Sensor 1
Sensor 4
Sensor 5
Inflow
Emptying Horapark facility
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Wat
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Improving the designGoal:Use Hydrus results and measurements to improve
the design
How to do it?Define the calculation of the infiltration capacity
(“the Out”)much better
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Improving the designImproving the infiltration model:
• Scientifically much more correct• Separate calculation of sides and bottom• Includes water level & suction of soil
Old New
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Improving the designTesting new infiltration model:
• Much better fit with Hydrus results• Excellent fit with measurements
Emptying of Horapark infiltration facility
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Time [h]
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Measurements
Darcy constant
Darcy dynamic
Valkenburg
Influence groundwater level
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-0.5 0 0.5 1 1.5 2Depth groundwater level below bottom [m]
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Darcy dynamicDarcy constantValkenburgHydrusHydrus no GWL
Comparing Hydrus with design method
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0.0 0.5 1.0 1.5 2.0 2.5 3.0Time [d]
Wa
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[cm
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Hydrus
Darcy dynamic
Darcy constant
Valkenburg
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Conclusions & recommendations
• The current design method is scientifically wrong.
• The biggest uncertainty is the infiltration capacity
• The infiltration capacity is mainly affected by the water level in the facility, groundwater level and the shape of the facility
• The refined design method with the refined infiltration model offers a more accurate design.
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Conclusions & recommendations
• Start measuring and monitoring in existing facilities
• Study the influence of the design of the facility
• Study the clogging process in and around the facility
• Study effects of extreme rainfall on the facility and tis surroundings
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Thank you for your attention!
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Borrel
In 15-20 minutes:Next to room 4.74
Tonight at 21.00:Café Belvedere at the
Beestenmarkt