Integrated bed-load and driftwood retention in Kien CH Findings from model based testing and the 2011 flood

Transcription

1 Integrated bed-load and driftwood retention in Kien CH Findings from model based testing and the 2011 flood Guido Lauber I Jürg Speerli 13th Congress INTERPRAEVENT 2016

2 Table of Contents I Chronology Floods between August 2005 Design of flood protection ( ) Model-based testing (2006) Execution of flood protection ( ) Flood on 10. October 2011 Findings and conclusion 2

3 Floods between August 2005 Rainfall in the Bernese Oberland Kiental had 200 mm rainfall in 3 Days ( August 2005) Kiental 3

4 Floods between August Bridge in Kien Blockage through sediment and driftwood Taken on the 22. August

5 Floods between August Chiene near Kien HQ 2005 = 120 m 3 /s Sediment Discharge 2005 = m 3 Driftwood Quantity 2005 = m 3 Bridge Kien Chiene 5

6 Floods between August Flooded areas of Chiene Villages Kien and Reichenbach Damages: ca. CHF 50 Mio. Reichenbach Kien (Bridge) Kander 6

7 LLE and design of protection measures ( ) Protection measures in Kien 7

8 LLE and design of protection measures ( ) Protection measures in Kien Bedload and driftwood retention 8

9 LLE and design of protection measures ( ) Protection measures in Kien Bedload and driftwood retention Enlarging of the Chiene 9

10 LLE and design of protection measures ( ) Protection measures in Kien Bedload and driftwood retention Enlarging of the Chiene Riverbed protection with fishfriendly stone weirs and ramps 10

11 LLE and design of protection measures ( ) Protection measures in Kien Bedload and driftwood retention Enlarging of the Chiene Riverbed protection with fishfriendly stone weirs and ramps Dam for overload 11

12 LLE and design of protection measures ( ) Protection measures in Kien Bedload and driftwood retention Enlarging of the Chiene Riverbed protection with fishfriendly stone weirs and ramps Dam for overload New bridge Cost: CHF 17 Mio. 12

13 Model-based testing ( ) HSR Hochschule für Technik Rapperswil Proof of functionality Optimising the protection measures Overload case Will subsequently be presented by Prof. Dr. Jürg Speerli 13

14 Execution of protection measures ( ) Bedload retention Retention of a minimum of m 3 sediment 2 Openings H x W : 0.75 m x 5.0 m Pool forming at 45 m 3 /s Overflow area EHQ = 200 m 3 /s 14

15 Execution of protection measures ( ) Driftwood retention 15 m in front of the bedload retention system Retention of a minimum of m 3 driftwood Completed 2010 Emch+Berger I HSR Hochschule Rapperswil Interpraevent 2016 I Dr. Guido Lauber I Prof. Dr. Jürg Speerli I

16 Execution of protection measures ( ) Driftwood retention system 10 m high und 1.0 m diameter concrete pillars Spacing: 2.70 m 16

17 Model-based testing ( ) Sedimentation mechanisms in the retention system Reduction of flow depth through enlargement of the channel Reduction of bedslope Water build-up and formation of pools in the retention system Direct obstruction of sediment path through the construction 17

18 Model-based testing ( ) Bedload output without driftwood Scenario: HQ 100 long Bedload input: m 3 Bedload output: m 3 Geschiebeaustrag [m 3 ] 70'000 60'000 50'000 40'000 30'000 20'000 Geschiebeaustrag pro Intervall Geschiebeaustrag kumuliert Gefahrene Abfluss-Ganglinie Abfluss [m 3 /s] 10' Zeit [h] 18

19 Model-based testing ( ) Bedload output without driftwood 19

20 Model-based testing ( ) Bedload output with driftwood Scenario: HQ 100 long Driftwood: m 3 Bedload input : m 3 Bedload output : m 3 20

21 Model-based testing ( ) Bedload output with driftwood 21

22 Model-based testing ( ) Positioning and dimensions of the retention system Short rake Long rake 22

23 Model-based testing ( ) Positioning and dimensions of the retention system A Abschlusssperre Rechen Schwemmholzteppich Abfluss unter Druck Auflandungskörper i = 3 % A Durchlasssohle = Fixpunkt 23

24 Model-based testing ( ) Positioning and dimensions of the retention system Short rake 24

25 Model-based testing ( ) Positioning and dimensions of the retention system Long rake 25

26 Model-based testing ( ) Positioning and dimensions of the retention system Height of dam with short rake Height of dam with long rake 26

27 Flood on 10. Oktober 2011 Impact comparison Flood 2011 Peak Discharge Bedload Driftwood 110 m 3 / s m m 3 Flood m 3 / s m m 3 27

28 Flood on 10. Oktober 2011 Impact comparison 28

29 Flood on 10. Oktober 2011 Impact comparison 29

30 Findings and conclusion Model-based testing Larger outlet opening Bedload output Driftwood Bedload output How to balance Safety and maitenance? Specifying the size of the outlet opening, positions and dimensions of the driftwood retention system, height of the dam (left-side) Proof of overload case 30

31 Findings and conclusion Flood October 2011 Bandwidth of driftwood quantities Reduction of sediment output after a driftwood blockage of the outlet opening Pool forming Bedload output Adjustment of the rake geometry Larger branches should be able to pass when the water levels rise Blockage of the outlet opening, reduction of bedload output during the floods end With a water build up all driftwood is retained 31

32 Thank you for your attention! Guido Lauber I Jürg Speerli 13th Congress INTERPRAEVENT 2016