Description
Baffles, or impediments, are arranged along the debris flow path first to promote the dissipation of the energy, to decrease the velocity of the debris flow and thereby to deposit avoiding huge impact on infrastructures located in the region of the debris-flow fan. Impediments can be either natural, such as threes, or artificial that can be constructed of earth, timber, or steel. They can be placed as single units, in lines or staggered. They can be used both by themselves but also commonly used in combination with other forms of control such as unconfined deposition areas (VanDine, 1996). In addition, baffles are commonly positioned in groups in front of rigid barriers to attenuate flow energy and reduce the impact induced on the rigid barrier.
Figure 1 Energy dissipating baffles along the channel Figure 2 Baffles positioned in front of rigid barrier in Hong Kong (Choi et al, 2014)
Advantages
- Easy and fast construction, low cost
Disadvantages
- Not enough to be effective, they need to be coupled with another type of mitigation measure
Design methods
Design considerations include the design magnitude or volume of the debris flow, likely flow path, potential runout distance, impact forces, and run-up (VanDine, 1996).
With regards to the baffle characteristics, baffle height, longitudinal spacing between successive rows, and the number of rows on flow impedance are relevant for the design effectiveness.
Figure 3 Schematic diagrams of the energy dissipation structure of cubic baffles (Wang et al, 2017)
Figure 4 Plan and oblique view of impediments to flow (baffles) (VanDine, 1996)
Functional suitability criteria
Type of movement |
||
| Descriptor | Rating | Notes |
|---|---|---|
| Fall | 3 | Will be updated soon |
| Topple | 2 | |
| Slide | 3 | |
| Spread | 2 | |
| Flow | 9 | |
Material type |
||
| Descriptor | Rating | Notes |
|---|---|---|
| Earth | 8 | Will be updated soon |
| Debris | 9 | |
| Rock | 4 | |
Depth of movement |
||
| Descriptor | Rating | Notes |
|---|---|---|
| Surficial (< 0.5 m) | 9 | Will be updated soon |
| Shallow (0.5 to 3 m) | 9 | |
| Medium (3 to 8 m) | 4 | |
| Deep (8 to 15 m) | 2 | |
| Very deep (> 15 m) | 0 | |
Rate of movement |
||
| Descriptor | Rating | Notes |
|---|---|---|
| Moderate to fast | 7 | Will be updated soon |
| Slow | 3 | |
| Very slow | 1 | |
| Extremely slow | 0 | |
Ground water conditions |
||
| Descriptor | Rating | Notes |
|---|---|---|
| Artesian | 7 | Will be updated soon |
| High | 9 | |
| Low | 4 | |
| Absent | 3 | |
Surface water |
||
| Descriptor | Rating | Notes |
|---|---|---|
| Rain | 8 | Will be updated soon |
| Snowmelt | 8 | |
| Localized | 4 | |
| Stream | 4 | |
| Torrent | 4 | |
| River | 4 | |
Reliability and feasibility criteria
| Criteria | Rating | Notes |
|---|---|---|
| Reliability | 5 | Will be updated soon |
| Feasibility and Manageability | 6 | Will be updated soon |
Urgency and consequence suitability
| Criteria | Rating | Notes |
|---|---|---|
| Timeliness of implementation | 7 | Will be updated soon |
| Environmental suitability | 4 | will be updated |
| Economic suitability (cost) | 6 | Will be updated soon |
References
Debris Flow Control Structures for Forest Engineering - D.F. VanDine 1- Res. Br., BC Min. For., Victoria, BC, Work. Pap, 8, 1996.
Experimental study on a debris-flow drainage channel with different types of energy dissipation baffles - Fei Wang, Xiaoqing Chen, Jiangang Chen, Yong You. 2017
Flume investigation of landslide debris–resisting baffles - C.E. Choi, C.W.W. Ng, D. Song, J.H.S. Kwan, H.Y.K. Shiu, K.K.S. Ho, R.C.H. Koo. 2014
Computational investigation of baffle configuration on impedance of channelized debris flow - C.E. Choi, C.W.W. Ng, R.P.H. Law, D. Songa J.S.H. Kwan, K.K.S. Ho. 2014
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