1
Burial
Deposition and burial on the downstream alluvial fan.
Types of debris flow Disasters
2
Erosion
Erosion of both sides of the stream channel and downcutting of the streambed.
3
Blockage
Narrow streams and low culverts are prone to blockage by sediment, rocks, or driftwoods.
4
Impact
debris flow possesses extremely strong impact force, easily destroying or penetrating structures.
5
Stream Diversion
The original stream channel is diverted due to debris flow deposition or bank collapse.
6
Abrasion
Concrete structures, such as levees and check dams, are worn down by debris flow.
7
Main Channel Constriction
The main channel is constricted by bank collapse on both sides and sediment carried in by tributaries.
Response Strategies for debris flow Disaster Types
| Debris Flow Disaster Type | Description | Response Strategies | |
|---|---|---|---|
| Hard Infrastructure | Soft Measures | ||
| Burial | Deposition and burial on the downstream alluvial fan | Stream Works, Ecological Engineering | Delineate debris flow potential areas, restrict development, and assist residents in downstream deposition zones with relocation or early evacuation to safe shelters |
| Erosion | Erosion of both sides of the stream channel and downcutting of the streambed | Stream Works | Restrict development on both banks and establish buffer zones; ensure early evacuation to safe shelters for residents on both banks |
| Blockage | Narrow streams and low culverts are prone to blockage by sediment, rocks, or driftwood | Dredge or clear the channel to prevent blockage, widen the channel, reduce the number of bridge piers, and increase the cross-sectional area of culverts | Monitor water levels and culvert blockage; promptly notify residents along susceptible channels for evacuation to safe shelters |
| Impact | Debris flow possesses extremely strong impact force, easily destroying or penetrating structures | Stream Works, Bridge Works | Assist residents in debris flow potential areas with relocation or early evacuation to safe shelters |
| Stream Diversion | The original stream channel is diverted due to debris flow deposition or bank collapse | Stream Works | Assist residents in areas prone to collapse or channel deposition with relocation or early evacuation to safe shelters |
| Abrasion | Concrete structures, such as levees and check dams, are worn down by debris flow | Stream Works, Slope Protection Works | Inspect engineering structures for damage that may reduce protective effectiveness |
| Main Channel Constriction | The main channel is constricted by bank collapse on both sides and sediment carried in by tributaries | Stream Works | Delineate debris flow potential areas, restrict development, and assist residents with relocation or early evacuation to safe shelters |
Applicable Engineering Methods for Sections of debris flow Potential Streams
| Section | Topographical Features | Phenomena | Mitigation Objective | Mitigation Mechanism | Applicable Engineering Method |
|---|---|---|---|---|---|
| Source Area |
|
Unstable sediment movement in the streambed and talus slopes | Prevent the occurrence of debris flow | Stabilize unstable streambed sediment | Series of sediment control dams and 『check dams』 |
| Gully collapse, 『landslides』 | Control the occurrence of gully collapse and 『landslides』 | Series of sediment control dams, retaining walls, slope protection works, etc. | |||
| Rainfall infiltration and surface runoff | Streambed dissipation and surface and subsurface drainage for slopes | Series of concealed dams, 『check dams』, drainage facilities, subsurface horizontal drainage, etc. | |||
| Transport/Runout Area |
|
debris flow impact | Prevent debris flow propagation/development | 1. Block boulders 2. Reduce flow velocity |
Permeable dams (slit dams, notch dams, grid dams, etc.), series of sediment control dams, semi-permeable dams |
| debris flow overflow | Raise and reinforce stream banks near overflow points | Revetments, foundation protection works, guide walls | |||
| Increasing debris flow volume | Consolidate streambed and banks, block sediment | Series of sediment control dams, 『check dams』, permeable dams, semi-permeable dams | |||
| Subsequent sediment-laden flow overflow | Appropriate engineering design and reduction of sediment deposition in the streambed | Dredging/Clearing, appropriate engineering design (e.g., reserving sufficient freeboard) | |||
| Driftwood | Block driftwood | Permeable dams, semi-permeable dams |
頁面頂端
