美工圖片   Investigation of Current Status in Bei-nan River System (Water Resources Planning Institute, WRA, MOEA. March, 2004)
 

The early work on the development and management of rivers was emphasized the construction of hydraulic facilities which were related to flood-control and water resource allocation, but the ecological protection was barely concerned. The current issue in the river management is how we can balance water utilization, flood-damage mitigation, and the recovery of the local natural environment. In the demand of river environment protection, we need to establish the basic ecological data to provide the river engineers for more ideal design.

“Investigation of Current Status in Beinan River System” was a two-year project, from 2002 to 2004, the mainstream and its five branches were detailed investigated. The results of the investigation not only provide more complete biological and ecological data for future management of the whole Beinan River basin, but also carry out the true goal of ecological engineering methods. The major achievements of this project were: habitat investigation, river biological composition, ecological resource database and Geographic Information Systems (GIS) on World Wide Web (WWW) querying system. Through the integrated data, we provide environmental protection index and suggestions for the river management.

On the habitat investigation, we believe that Beinan River is one of the few rivers with good water quality and abundant natural resources in Taiwan. We suggest that we need to preserve the giant stones in the middle of the river, since the giant stones will reduce water velocity, prevent erosion, and provide deep pools. Because channelized branch will increase the discharge loading of the mainstream and obliterate the natural flood-prevention function, we should prevent river branch from channelization.

The detailed species are sorted as below:

Fish 09 family 24 species
Shrimp 02 family 13 species
Crab 02 family 04 species
Benthos 35 family 70 species
Shellfish 08 family 10 species
Alga 36 family 89 species
Plant 105 family 373 species
Mammal 11 family 17 species
Bird 38 family 112 species
Reptile 08 family 24 species
Amphibian 03 family 11 species
Insert 16 family 53 species

 

The channelized branch in Beinan River System

The river biological composition investigation revealed that the environment of the Beinan River was more stable in the midstream, and also the habitat was more diversified, thus more species could be preserved in midstream. In the branches, we found large-sized fishes and more species in the reserve area. The compositions and distributions of the fauna and flora in Beinan River system are largely affected by environmental factors. In general, a more stable environment will be more suitable for more diverse and plentiful creatures.

The databank contained natural, artificial environment data, biological resources data, and other reference documents, video, and pictures. According to the raw databank, we established GIS on the WWW. The investigation data is easy to be retrieved, re-analyzed, re-present in geological layer concept for all users through Internet.

In summary, we have some suggestion for the management of the Beinan River:

1.  Manage and plan the drainage area. By analyzing the landforms, one could plan the best way the stream goes, and dredge the mainstream when necessary via making quarrying sand open to public use.

2.  Regenerate the islet in the middle of the river. The islet can control the center of flow, be the habitat for animals, and absorb heat by its vegetation.

3.  Construct natural dikes. At the moment the riverbank without dikes is on the fault area, the authority should make more investigation before construct new levees.

4.  Maintain and modify former dikes. The authority should consider the flood tractive force, choose different materials to improve the surface of the dike, and make safety as the first priority in planning.

5.  Raise the ratio of the basic research and planning in the engineering. The most serious problem in river engineering in Taiwan is insufficient basic research, only have the sufficient environment data could the engineers make good quality works. (In Japan, the ratio of previous research and design is over twenty-five percent in the whole project budget, and the previous investigation usually takes more than five years.)