MSc Thesis presentation: Rethinking the design of infiltration facilities

1. MSc Thesis presentation:Rethinking the design of infiltration facilities Leon Valkenburg

2. 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) MSc thesis presentation Leon Valkenburg

3. Outline • Urban drainage problems • Storm water infiltration • The design • Studying infiltration facilities • Improving the design • Conclusions and recommendations MSc thesis presentation Leon Valkenburg

4. Urban drainage problems Problem 1: Pluvial flooding (wateroverlast) MSc thesis presentation Leon Valkenburg

5. Urban drainage problems Problem 2: Sewage spills (riooloverstorten) MSc thesis presentation Leon Valkenburg

6. Urban drainage problems Rain Solution? Water goes to sewer Storm water infiltration Too much water: flooding Unsaturated zone Groundwater MSc thesis presentation Leon Valkenburg

7. Storm water infiltration Summarising 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 MSc thesis presentation Leon Valkenburg

8. Storm water infiltration Surface facility Types of infiltration facilities Subsurface facility Combined facility MSc thesis presentation Leon Valkenburg

9. Storm water infiltration Infiltration depends on: • Soil type • Water level in facility • Groundwater level • Rainfall history • Temperature • Clogging rate Animation MSc thesis presentation Leon Valkenburg

10. The design How 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? MSc thesis presentation Leon Valkenburg

11. The design Current design practice • Design rainfall: depth-duration-frequency curves • Infiltration capacity: use Darcy’s law MSc thesis presentation Leon Valkenburg

12. The design Current 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! MSc thesis presentation Leon Valkenburg

13. 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 MSc thesis presentation Leon Valkenburg

14. Studying infiltration facilities Modelling: • 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 MSc thesis presentation Leon Valkenburg

15. Studying infiltration facilities Modelling What can you do with the results? • Find “the out” in various circumstances • Test the current design model MSc thesis presentation Leon Valkenburg

16. Studying infiltration facilities Measurements 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 MSc thesis presentation Leon Valkenburg

17. Studying infiltration facilities The location of Ede MSc thesis presentation Leon Valkenburg

18. Studying infiltration facilities Measurements in Ede Two facilities tested: • A soakaway from 1980 • An infiltration unit from 2001 Test the performance by measuring: • Water level in facility • Soil moisture content: amount of water in the soil MSc thesis presentation Leon Valkenburg

19. Studying infiltration facilities Measurement setup • Fill with tank truck • Measure water level with diver • Measure soil moisture with sensors MSc thesis presentation Leon Valkenburg

20. Studying infiltration facilities Photo impression MSc thesis presentation Leon Valkenburg

21. Studying infiltration facilities Measurement 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 MSc thesis presentation Leon Valkenburg

22. Improving the design Goal: Use Hydrus results and measurements to improve the design How to do it? Define the calculation of the infiltration capacity (“the Out”) much better MSc thesis presentation Leon Valkenburg

23. Improving the design Improving the infiltration model: • Scientifically much more correct • Separate calculation of sides and bottom • Includes water level & suction of soil Old New MSc thesis presentation Leon Valkenburg

24. Improving the design Testing new infiltration model: • Much better fit with Hydrus results • Excellent fit with measurements MSc thesis presentation Leon Valkenburg

25. 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. MSc thesis presentation Leon Valkenburg

26. 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 MSc thesis presentation Leon Valkenburg

27. Thank you for your attention! MSc thesis presentation Leon Valkenburg

28. Borrel In 15-20 minutes: Next to room 4.74 Tonight at 21.00: Café Belvedere at the Beestenmarkt MSc thesis presentation Leon Valkenburg