«by: MA. ALETHA A. NOGRA Civil Def fense Offic III cer Office of Civil D e Defense-Departmen of Natio Defen nt onal nse R Republic o the Philippines ...»
The combination of main weir and bypass channel serves to control both floods and drought. The main weir is composed of ten units of two-stage steel roller gates which is capable of controlling a great amount of discharge mainly to prevent flood. Its bypass channel which is a pair of conduits of 15 cm and 5 m wide is equipped with three-stage steel roller gates, with a flow controlling valve and hydraulic power generation facilities installed at the end, and is capable of controlling a small amount of discharge with great precision, primarily to prevent drought.
The flow controlling valve can discharge up to 8 cubic meter per second. The main weir can only control a large discharge of water while the valve works automatically to prevent fluctuations in the discharge and the small changes in the water level of Lake Biwa. According to the Lake Biwa Development Project, the available low water level is -1.5m and the discharge becomes impossible when the water level is less than -1.3m.
The gates are to be opened for discharge but a precise control of flow is difficult in this method that is why a bypass channel is installed in order to make a precise control of flow rate even if the water level goes down. Using a part of the discharge from the bypass channel, the power generation for management by low head is conducted.
The weir controls the amount of water by overflowing the gates. When the main weir gate is in the mode of touched bottom, both upper and lower gates are attached to the bottom, and the maximum flow in the overflow situation is discharged. In this mode, the precise control of flow is impossible. The fluctuation of water level in the upstream changes overflow water depth, which leads to a variation of flow. Full open mode is the situation when upper and lower gates are moved up above the water surface, and Seta river flows naturally in this mode. The discharge sharing has four components namely main weir, bypass, controlling valve and power generation facilities which play a role with each other.
There are buildings for management, electricity, facility, discharge remote control facility, alarm facility, observation facility, and communication facility established in order to manage the Seta River Weir. The building for management is constructed with Lake Biwa River Office which is adjacent to Seta River Weir. The office is consists of a branch operation office and the control building.
The branch operation office or Aqua Biwa was established in March 1992 as a facility for the people to learn flood control and water utilization of Lake Biwa and Yodo river, as well as to promote and spread the related scientific knowledge.
There are various observation facilities for observation and monitoring of the weather with large differences between the north and south areas because the weather in the Lake Biwa area shows a clear difference between the north and the south. There are a number of information service facilities providing information of water level at Lake Biwa for its users. There are three facilities for remote controlling, information processing and safety confirmation. The discharge control system functions to remote-control each gate automatically or manually. The disaster prevention information system stores collected data on hydrology and water quality as well as statistics process and various simulations. There are also CCTV facilities installed to confirm safety of weir operation and monitor moves of each gate. The alarming facility includes nine stations with sirens around the weir, at the upstream and downstream areas. Furthermore, to ensure that the water will be discharged safely, patrols go along the river, on foot and in warning cars, to carry out safety checks and before the discharge operation, a siren will alarm to give a warning.
There are seven water level gauging stations for monitoring the water level of Lake Biwa with the oldest station monitoring for 130 years way back 1874 under the guidance of a Dutch engineer. Since it is difficult to grasp the water level at only one station, it is determined that the water level of Lake Biwa shall be the mean value of the water level at the five gauging stations according to the River Weir Operation enacted in March
1992. Standards for the water level control of Lake Biwa are thus set up by the Regulations of the Seta River Weir Operations. The water level of Lake Biwa is controlled to maintain to maintain Lake Biwa Surface Level at +0.3m during the non-flood period, and -0.2m or -0.3m lower than surface level at the flood period in order to bring the highest water-level down during the flood. In case of drought, availing the water level of -1.5m, it supplements public water, industrial water, agricultural water, and river maintenance discharge, which are needed in the downstream of Yodo river.
During the flood season, the water level of Lake Biwa is lowered by -0.2m or -0.3m in advance to bring down the highest water level at a flood time under the “Transition Operation” which is carefully done so that a sharp change of the water level is avoided.
Hence the operation of the Seta River Weir is classified into two: during flood for the prevention of flood around Lake Biwa and reduction of flood discharge in the downstreams; and the other is during the ordinary low water period like water-level maintenance of Lake Biwa and supplement of water to the downstream. During the ordinary or low water level, the weir is operated to control dams at Yodo River system and Lake Biwa so that water will be use efficiently. The weir is operated daily based on the intake situation necessary for public water and industrial water consumption in the downstream of Yodo river.
During the flood, the discharge at the Uji and Yodo rivers is restrained or the weir is completely closed, thus the flood control is made in the downstream. Then the Seta River Weir is fully opened after the increase of water in Kizu and Katsura rivers is stopped. The water level of Lake Biwa is refrained from increasing and is lowered. At the Amagase dam, a preliminary discharge is made when a flood is expected in order to secure the flood storage (pocket to store flood) and for smooth operation of the preliminary discharge from the weir is restrained. When the flow rate at the point of Amagase dam exceeds 840 cubic meter per second, Amagase dam makes flood prevention for Uji river through flood control. In this case, the Seta River Weir is completely closed from when flow rate into Amagase Dam exceeds 840 cubic meter per second until when it becomes less than 840 cubic meter per second. Since the water level at the Hirakata point of the downstream of Yodo river exceeds +3.0m until the lowering of water level is confirmed, the weir is completely closed. In order to be ready for a coming flood, Amagase Dam discharges the water stored for flood control and lowers to the limited water level. The discharge from the weir is limited in order to shorten the time for operation. Once the flow of Kizu and Katsura rivers has ceased increasing, the Seta River Weir is fully opened to restrain a rise of the water level at Lake Biwa and then to bring it down. The Lake Biwa Development Project designates -1.5m as the usable low water level of Lake Biwa and develops 40 cubic meter per second of water for use. During drought and the water level goes down, users of water in the downstream of Yodo river, the Kinki Regional Development Bureau, Osaka, Hyogo, and Shiga Prefectures convene the “Yodo River Drought Control Conference” and coordinate measurements against drought. The Minister of Land, Infrastructure, Transport and Tourism decides what measures to take after hearing the opinions of the concerned governors.
Development and preservation of river environments. The operation of Seta River Weir has also taken into consideration the diverse species living in the river, its impact on fish in spawning, growth and increase. The Seta River Weir is operated in such a way to prevent death of fishes from failing to escape and drying up river water in lower reaches.
F. The Role of Learning Institutions in Creating a Culture of Safety in the Community: Disaster Reduction and Human Renovation Institution One of the major factors in institutionalizing a culture of safety among the citizens is the establishment of a Disaster Reductions Institute. The DRI or the Disaster Reduction and Human Renovation Institution is also known as the Great Hanshin-Awaji Earthquake Memorial. The DRI was founded by Hyogo Prefecture in April 2002 with the support of the Japanese government. It is being supervised by the Hyogo st Earthquake Memorial 21 Century Research Institute. The DRI aims at cultivating disaster prevention culture, mitigating social vulnerability, and developing policies for disaster reduction by transferring experiences of the Great Hanshin-Awaji Earthquake and applying lessons learned from the Earthquake for the better future, thereby contributing to realizing a safer and more secure civil society along with education regarding the value of life and the preciousness of co-existing. Aside from this, the DRI also aims to be an international research and study hub, which contributes to disseminating information on effective measures for all types of disasters.
Disaster Reduction and Human Renovation Institution
Museum Exhibits. The DRI features actual experiences and lessons learned from the Great Hanshin Awaji Earthquake. This is in collaboration with disaster victims themselves, local citizens and volunteers. The museum is open for the rest of the world to learn from, especially for the children who are to create a future. The knowledge gained from this is for the children to consider in every decision they make so as to contribute in making a resilient society. Through this institution, DRI motivates citizens and visitors and visitors to take a sincere interest in, deliberate upon, and understand the importance of disaster reduction, precious human life, and the value of mutual dependence of people.
Action Research on Disaster Reduction and Development of Disaster Reduction Professionals.
As DRI adequately understands the challenge for public entities based on the experiences of the Great Hanshin-Awaji Earthquake as well as on academic research achievement. DRI conducts action research that contributes to he formulation and implementation of disaster reduction policies and management actions by central and local governments, communities, and business enterprises. In addition, DRI takes a lead role in promoting and increasing the value of such practical research approaches within the academic arena. For a widespread disaster reduction awareness within society, DRI provides practical research for the improvement of disaster reduction
abilities. There are ten research fields identified as follows:
Governmental disaster management Emergency evacuation measures Secondary disaster measures Logistics of material resource Information measures Volunteer Infrastructure Care for victims Local economy Important areas for research are considered while attempting to plan for the next 30 years, DRI takes on into consideration present social demands along with their overall mission statement. This is often done by continuous and systematic updating of the organizational roadmap every 5 years to reflect important areas for research and the research that should be addressed. Important areas of research are also focused on the optimization of post disaster response as it relates to individuals and society;
improvement of inter-organizational cooperation policies to cover disasters tat span wide areas; and building strategies for restoration and revitalization of regional communities. The Institute has also established “improving Society’s Ability to cope with Large-scale disasters” as the Institute’s core research theme which is to be continued over a fixed term. “Special Research Projects” flexible and mobile research themes established to dig deeper into the development of related areas of the “Important Areas of Research”. Groups or all full-time researchers are involved in this project over fixed terms. In fostering full-time researchers, the Institutes encourage candidates with a Master or Ph.D. degree as eligible for employment for 3-5 years as a full-time researcher. Under the direction of senior researchers, they are then able to work on practical disaster prevention research and participate in the various other businesses of the center which is also a part of their training to become practical disaster prevention experts.
Collection and Preservation of Source Documents and Materials.
DRI works in association with local citizens and communities to continuously collect information on the Earthquake and disaster reduction, as well as in the development of its database. This is primarily aimed to ensure that the profound feelings of disaster victims and the lessons of the Great Hanshin-Awaji Earthquake do not fade from our memory. DRI in turn displays and disseminates this information in a manner which is a lot easier to understand especially for ordinary citizens.
Headquarters Assistance in Disaster Response.
DRI also dispatches experts with practical and systematic knowledge in disaster response especially in case of large scale disasters. These dispatched experts will provide appropriate information and advice to headquarters managers, thereby contributing to mitigation of further damage as well as in preparation for recovery and reconstruction.
Training of Disaster Managers and Practitioners.
DRI likewise conducts training of local government practitioners who play central roles in disaster management. In these training programs, DRI share the experience of the Great Hanshin-Awaji Earthquake. DRI has a systematic and comprehensive program on practical knowledge and skills in disaster reduction with reference to the latest research result. Through this training program, DRI aims to contribute to the upgrading of emergency management capacity of the local governments. DRI has two kinds of training programs being offered namely, Intensive Course and International Training Course. Intensive Course is focused on specific theme and central purpose.