三重県四日市市にて小川の修復工事を行わせていただきました。
Streams are natural waterways, smaller than rivers, that are formed in the landscape by precipitation and groundwater. The formation of streams is influenced by several natural phenomena, including
Topography
Topographic shape and elevation play an important role in creek formation. Streams tend to form in low-lying areas, following the path of least resistance and flowing downstream along valleys and ravines.
Rock Types
Different rock types erode at different rates, which can affect the flow and shape of streams.
Climate
The climate of the area can also influence the formation of the creek. Streams in areas with high precipitation tend to change course more rapidly.
Geology
The geology of an area, such as the presence of faults and fractures, can influence stream formation by affecting groundwater flow and erosion patterns.
Human Activities.
Human activities such as land use change, dam construction, and deforestation can also affect stream formation by altering the natural water balance and causing changes in flow and sedimentation patterns.
Under natural conditions, streams normally maintain a stable channel shape due to erosion and sedimentation forces, but human activities and heavy rainfall can alter the balance and cause changes in the stream channel.
The damage to the creek this time was caused by last year's heavy rains, which had washed a large amount of sediment into the creek.
To restore the flow path, the soil is dug out while keeping track of the original depth and width. It is also easier to manage the stream if you know how the flow rate changes with the seasons.
Restoring the creek to its natural state may be necessary to ensure its health and stability. Stream restoration also requires careful investigation.
An assessment of the damaged stream channel will be conducted to determine the extent of the damage, its causes, and potential solutions.
Develop a detailed design for the desired channel configuration and restoration.
Prevent erosion and create a stable base for restoration efforts.
Install sandbags and erosion control structures to prevent erosion and improve water flow, while adapting the river channel to its natural flow, if necessary.
Survey the stream banks to determine what vegetation is growing along the banks and whether it can be regenerated in order to fix the soil, provide wildlife habitat, and reduce erosion.
Implement a regular maintenance program to maintain the stability and health of the restored stream channel.
Regularly monitor the restored stream channel to assess its health and identify areas in need of additional work.
After construction, the vegetation that would serve as soil retention was not established, and the dug-out soil was made into vegetated sandbags and piled on the banked area.
The sand and gravel in the creek and the clay layer in the bottom soil are indicators of digging. In addition, the original topographic area may have many buried seeds, so vegetation recovery will proceed quickly.
In streams, under natural conditions, water and sediment are constantly moving, altering the shape of channels, bars, and pools.
Puddles can form as the water slows down in certain areas, increasing the depth of the water and creating deeper stillwater areas. Puddles form in streams for several reasons, including the presence of natural obstacles such as large rocks or boulders that impede the flow of water, slowing or deepening the flow of water. Puddles can also be created by erosion, sedimentation, or other changes in the creek bed or stream channel that alter the flow of water. (In this case, sandbags were placed)
Install sandbags to control water flow so that water flows gently into the biotope from the lower right.
To control the flow of sand and mud, we also create a sedimentation basin (chinsachi) and so on.
There are many places where ecosystems can be successfully managed by human intervention, and rare plants and animals can be found in these biotopes. There are many biotopes in Mie Prefecture, but some have fallen into disrepair due to lack of management, and many have been invaded by non-native species.
Schlegel's green frog in hibernation. By combining human power and a jumbo, we can also protect precious lives.
By maintaining as many biotopes as possible in a healthy state, we hope to preserve them as valuable places where a variety of living creatures are active from the viewpoint of preserving biodiversity.
Please feel free to contact Prunery Sora for biotope management and biological surveys in Mie Prefecture.