Research Trends and Results
Upgrading Inspection and Management Methods for River Management
Facilities
SUGIHARA Naoki, Research Coordinator for Integrated Water Disaster Management
River Department
HATTORI Atsushi (D.Eng.), Head; MORI Hirotoshi (D.Eng.), Senior Researcher; FUKUHARA Naoki ,Researcher
River Division, River Department
Keywords: river levee, maintenance, inspection, patrol
1. BackgroundOf the 10,216 river management facilities (dams, watergates, sluices, sluice pipes, etc.) in the rivers administeredby the country, as many as 3,765 facilities wereconstructed more than 40 years ago. The number ofsuch old facilities is expected to continue to increase anddeterioration is anticipated to accelerate in many of them.
The river administrators are monitoring the conditionof river management facilities by conventionallyconducting "inspections" (1 or 2 times a year), in-depth
visual observations on foot, and "patrols" (comprehensive
visual inspections 1 or 2 times a week, mainly from a car).
They have maintained the functions of river management
facilities and ensured flood control safety by detecting
deformations as a sign of early damage and repairing
facilities as required.
In the future, the number of deformations that will bedetected is expected to increase in accordance with theincrease in deteriorating river management facilities.
Accordingly, efforts and time required for maintenancewill also increase and, under the present maintenancesystem, functional maintenance of river management
facilities may become difficult.
Therefore, it isnecessary to review the present inspection and patrol
methods in the interest of upgrading the maintenance ofriver management facilities.
2. Technical perspectives
Conventionally, river administrators have conductedmaintenance by monitoring the condition of facilities but
on1y sporadically applied new technologies in order torationalize their maintenance methods. They have notsteadily studied enough to make continuous
improvements based on actual condition using
accumulated data on deformations and repairs.
In view of such circumstances, the MLIT started
building a river maintenance database to record the places,types, scales, etc. of deformations found throughinspections and patrols. With this database, the data thatwas previously managed separately by each riveradministrator will be collected and placed underintegrated control.
Taking this opportunity,
maintenance of river management facilities should bestreamlined by analyzing and evaluating this vast amountof data and incorporating results into site inspections andpatrols.
For example, one possibility is to construct a PCDA
cycle to streamline maintenance by first identifying
locations susceptible to deformation from thedeformation history and characteristics of rivermanagement facilities. Then, by strengthening theinspection and patrol and grasping the type and scale ofdeformation that is likely to degrade the flood control
safety of river levees and so forth, it should be easier todetermine whether repair is required or not.
3. State of study for upgrade
As part of the study for upgrading the maintenance ofriver management facilities, we are collecting dataobtained from the inspection and patrol of river levees infive rivers to analyze and evaluate the status of thosestudies. As a result, so-far unknown characteristics ofinspections and patrols have begun to become clear. For
example, the number of deformations found by one
administrator in one day is about 150 times those foundin a patrol, although there are variations according toriver.
Moreover, we have just begun to quantitatively
evaluate as well the decrease in flood control safety oflevees caused by deformation. It was found from thisevaluation that once a crack occurs in a river levee, thesafety factor for sliding decreases about 10 to 20% ascompared with a case of no deformation, although it
depends on the location of the crack and the nature of thesoil of the levee.
Note that, to identify locations susceptible todeformation from the deformation history andcharacteristics of river management facilities, we areusing a statistical processing method that has remarkably
advanced in recent years, but we are still working on it.
We will continue to study and would like to upgrade
maintenance by searching for desirable methods ofinspections and patrols, in order to prepare against theaccelerating deterioration of river management facilities.