IMPACT Breach Physical Modelling Review, Summary, and Objectives

1. IMPACT ~ Breach Physical Modelling Review of Modelling Work Undertaken So Far...

2. IMPACT - Breach Physical Modelling Summary • Objectives • General approach and facilities • Scaling • Controlling / assessing soil properties • Data collection • Test programme • Test results so far...

3. IMPACT - Breach Physical Modelling Objectives To provide lab data through which: • Field test data may be compared and scaling issues (between field and lab) analysed • Breach formation behaviour may be extrapolated from field test data via multiple lab tests showing effect of variation in: – geometry / sediment size & grading / construction / embankment condition • Additional data for numerical model comparison and validation

4. IMPACT - Breach Physical Modelling General approach and facilities: General approach: • Programme of 25 lab tests – 9 Autumn 2002 – 8 Spring 2003 – 8 Autumn 2003 • Scaling field tests at 1:10 (trying to balance scaling effects) • Using large scale laboratory facilities to extend data sets as much as possible

5. IMPACT - Breach Physical Modelling General approach and facilities: Facilities: • Using a large flume (50m x 10m wide) • Peak discharge >1m3/s (but limited) • Automated logging of: – water levels – flow into flume – pressure beneath embankment – u/s vertical velocity profile – u/s face digital photo shots – d/s face video footage

6. Breach Formation Physical Modelling Flume (earlier model)

7. Breach Formation Physical Modelling Flume (dimensions) 10m 50m 0.8m Flow upto 1.25m 3

8. IMPACT - Breach Physical Modelling Flume

9. IMPACT - Breach Physical Modelling Flume

10. IMPACT - Breach Physical Modelling Scaling • Range of approaches considered – Mobile bed modelling – Sediment entrainment / fall velocities – Reynolds, Froudian etc. • For non cohesive, considering different approaches, concluded straight geometric scaling – 1:10 • Review of scaling later within uncertainty assessment

11. IMPACT - Breach Physical Modelling Scaled Sediment

12. IMPACT - Breach Physical Modelling Scaled Sediment

13. IMPACT - Breach Physical Modelling Scaled Sediment

14. IMPACT - Breach Physical Modelling Controlling and Assessing Soil Properties In order to ensure that field and lab tests are similar we need to consider: • Soil type – grading – permeability – strength – cohesion • Construction properties: – density – moisture content

15. IMPACT - Breach Physical Modelling Controlling and Assessing Soil Properties Soil type (grading, strength etc.) is determined through lab analysis of the sample. Properties analysed include: – grading – permeability – proctor

16. IMPACT - Breach Physical Modelling Controlling and Assessing Soil Properties This data permits plotting of the density moisture curve to show optimum compaction. During construction, optimum compaction is aimed for. During construction density readings are taken (nuclear density probe) at 9 locations across the bank and at three levels. This permits the degree and consistency of compaction to be identified. (Test#1 1.79g/cm 3 ; Test#2 1.76g/cm 3 )

17. IMPACT - Breach Physical Modelling Density Measurement - Nuclear Probe

18. IMPACT - Breach Physical Modelling Data Collection Automated logging of: – water levels – flow into flume – pressure beneath embankment – u/s vertical velocity profile – u/s face digital photo shots – d/s face video footage

19. IMPACT - Breach Physical Modelling Data Collection

20. IMPACT - Breach Physical Modelling Data Collection

21. IMPACT - Breach Physical Modelling Data Collection

22. IMPACT - Breach Physical Modelling Test Programme Programme of 25 lab tests • 9 Autumn 2002 – Non cohesive – Prior to Autumn 2002 field work • 8 Spring 2003 – Cohesive – Prior to Autumn 2003 field work • 8 Autumn 2003 – TBA (piping?) – Post Autumn 2003 field work

23. IMPACT - Breach Physical Modelling Test Programme - Autumn 2002 • Lab Test#1 Trial / test experiment • Lab Test#2 Steeper sediment grading - D 50 Field Test#2 • Lab Test#3 Repeat Lab Test#2 • Lab Test#4 Breach location (initiate at side of channel) • Lab Test#5 Scaled grading of Field Test#2 • Lab Test#6 Vary geometry (Crest 2m, Slope 1:2) • Lab Test#7 Vary geometry (Crest 3m, Slope 1:2) • Lab Test#8 Steeper grading, different D 50 • Lab Test#9 SS Seepage or 2 nd D 50 variation

24. IMPACT - Breach Physical Modelling Test Programme - Spring 2003 Programme to be agreed. Objectives to: • Integrate with Norwegian field work • Integrate with other European and US experimental work

25. IMPACT - Breach Physical Modelling Test results so far... • Tests 1-5 completed (probably!) • Tests 6-9 within next 2-3 weeks • Steady state seepage an issue • Data from first tests yet to be processed, however photo and video footage is available...

26. IMPACT - Breach Physical Modelling Test results so far... Breach features noted in Tests 1-3: • (Seepage and slumping of d/s face) • Initial vertical cut through bank – Rapid cut back of d/s face in line with ‘slot’ – Likely significant erosion below ‘bed’ level • Vertical sides of breach • Side cracking and slumping • Upstream slope (face) remains in place as weir for considerable time (flow control)

27. IMPACT - Breach Physical Modelling Test results so far... Still photo series Test 2 Still photo series Test 3 AVI footage Test 2 AVI footage Test 3