Rethinking the design of infiltration facilities MSc Thesis presentation: Rethinking the design of...

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)



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Rain

Water goes to sewer


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

0

5

10

15

20

25

30

35

-0.5 0 0.5 1 1.5 2Depth groundwater level below bottom [m]

Re

lati

ve

dis

ch

arg

e [

-]

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

0

25

50

75

100

0.0 0.5 1.0 1.5 2.0 2.5 3.0Time [d]

Wa

ter

lev

el

[cm

] Hydrus

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

0.00

0.10

0.20

0.30

0.40

0.50

0.0 5.0 10.0 15.0 20.0Time [h]

So

il m

ois

ture

co

nte

nt

[-]

Sensor 1

Sensor 4

Sensor 5

Inflow

Emptying Horapark facility

0

40

80

120

160

0.00 5.00 10.00 15.00Time [hour]

Wat

er le

vel

[cm

] Water level


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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

0

40

80

120

160

0.00 4.00 8.00 12.00 16.00 20.00 24.00

Time [h]

Wa

ter

lev

el

[cm

]

Measurements

Darcy constant

Darcy dynamic

Valkenburg

Influence groundwater level

0

5

10

15

20

25

30

35

-0.5 0 0.5 1 1.5 2Depth groundwater level below bottom [m]

Re

lati

ve

dis

ch

arg

e [

-]

Darcy dynamicDarcy constantValkenburgHydrusHydrus no GWL

Comparing Hydrus with design method

0

25

50

75

100

0.0 0.5 1.0 1.5 2.0 2.5 3.0Time [d]

Wa

ter

lev

el

[cm

]

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

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