Tadaharu Ishikawa

Sustainable design of sanitation system based on material and value flow analysis for urban slum in Indonesia

Material flow analysis (MFA) and value flow analysis (VFA) were applied to the sanitation system in an urban slum in Indonesia. Based on the results of the MFA and VFA, garbage and excreta disposal costs were evaluated to be 0.7% and 1.1%, respectively, of per capita income. Such value flows seem reasonable in light of the recognized affordability to pay (ATP) standard. However, current excreta disposal methods create negative impacts on downstream populations. Because such disadvantages do not go back to disposers, but passed to downstream, the current value flow structure does not motivate individual toilet users to install treatment facility. Based on current material and value flow structures, a resource recycling sanitation system scenario was examined. Based on VFA, an affordable initial cost for such a system was calculated; this was found to be comparable in price to a cheaper composting toilet that is currently available in the market.

Benthic and interfacial mixing in a strongly-stratified estuary

Tone River is a shallow, tidal estuary with a controllable upstream freshwater discharge via a barrage. The mixing characteristics in the benthic and interfacial regions of the Tone River estuary were investigated during a time window of maximum freshwater discharge and high shear, using temperature and velocity microstructure measurements. Although the production of turbulent kinetic energy from mean shear was high throughout the water column, the intermittency of both up- and down-gradient buoyancy fluxes resulted in negligible net down-gradient mixing. These opposing fluxes were incorporated into a turbulent closure scheme by using the concept of percentage down-gradient flux. A comparison of vertical diffusivity from two alternative closures suggests that the stratification imposed a length scale limitation on the vertical turbulent excursions that proved crucial for the transition region between the benthic and interfacial regions; it is argued that a Richardson-number based closure is both conceptually and practically adequate to represent the effect of length-scale limitation and percentage down-gradient flux.

Flood Flow Analysis on Aerial Photos by Image Correlation Method with Support of Stereo Visualization

Stereo images of flood flow in river channels taken by airplanes contain a lot of useful information for river engineering works. The image correlation analysis (ICA) on a computer, which is a standard technique for stereo image analysis, sometimes produces anomalous results because the color patterns to be traced on the flood water surface are not very clear. On the other hand, a classical manual analysis (CMA) through a stereoscope usually works well even in such condition by the excellent perspective sensitivity of human eyes. But the CMA needs much more labor and time than ICA. In this study, a new technique was developed for analyzing the stereo images of river freshets by combining the above mentioned two methods: A small amount of suggestions made by the CMA are sent to a computer to improve the ICA results. The proposed method was applied to the aerial photos of a flood of the Tone River in Japan. Comparison of the analytical results from two sets of stereo images carried out independently showed that the proposed method gives high accurate result with less labor cost.

New Approach for Estimation of Pollutant Load by Using Artificial Neural Network

Pollutant load transported by rivers from non-point sources in watersheds is the major cause of eutrophication of closed water bodies such as lakes, reservoirs, and inner bays. Because it concentrates in a short time of flood event, regular water sampling cannot be adequate to monitor it. This study proposes a new type of monitoring technique of pollutant load in rivers: Optical characteristics of river water are monitored by a multi-item optical device. The relation between the sensor signals and the water qualities obtained from occasional sample analysis is modeled by Artificial Neural Network (ANN). After then, the time series of pollutant load can be produced from the optical signals. Field experiments were conducted in seven rivers flowing into Lake Kasumigaura. The ANN model trained by the data obtained in the year 2005 successfully produced the time series of pollutant load observed in the years 2006 and 2007. ANN models worked well in watersheds of different land use conditions if it was trained by the data obtained in each river.

Experiment of a Resource-Oriented Agro-Sanitation System for Urban Slum Area: Case of Indonesia

This chapter describes case study of applicability assessment for resource-oriented agro-sanitation business for urban slum in Indonesia, based on interdisciplinary field survey, (1) economic feasibility assessment, (2) demand potential assessment, and (3) social acceptability. The value flow analysis evaluated garbage disposal cost and excreta disposal cost at 0.7 and 1.1%, respectively, of household income, which represents a reasonable cost to disposers. However, under the current disposal scheme, negative value due to excreta disposal to river appears to be passed on to downstream populations. The structure of this value flow indicates that little attention is paid to the negative externalities, indicating that a solution in this case may be difficult to obtain. The affordable initial cost of a new resource recycling system was evaluated and compared with the costs of a currently available compost toilet by evaluating equipment lifetimes and potential income streams available from the sale of human excrement fertilizers. To estimate a value for the human excrement fertilizer, real-world case study in Indonesia, in which money was paid in exchange for human urine, was referred to. The evaluated affordable initial cost derived was sufficiently comparable to the price of a cheaper composting toilet currently available in the market. This implies that such a resource recycling system is feasible even in an urban slum. Results of demand and supply assessment showed that if resource-oriented sanitation system was diffused, supply would excess demands in the circle of 32 km radius, therefore cost discussion should assume more than 32 km transportation. According to the results of case estimation of tea plantation, total cost for fertilizer provided by resource-oriented sanitation system is possibly competitive to the normal price of synthetic fertilizer. However, if compared to subsidized price for low-income farmers, it seems difficult to compete. Regarding social aspect, the context of Islamic law is important. Islamic authorities regarded the resource-oriented sanitation system as no problematic concept and acceptable in the context of Islamic law.

Assessment of flood risk management in lowland Tokyo areas in the seventeenth century by numerical flow simulations

Numerical simulations using the shallow water model on an unstructured triangular mesh system were conducted to elucidate the hydraulic functions of the Nihon levee system, which was built in the seventeenth century to protect the city of Edo (present-day Tokyo) against flooding. Because numerical data related to the topography and hydrology of that era do not exist, simulation conditions were inferred from records from the beginning of twentieth century and recent GIS elevation data and flood records. In the simulation results, floodwaters spread over the floodplain surrounded by the levee system, and the inundation areas expanded gradually through a canal to rice paddies in the adjacent river basin. Furthermore, the rise in the water level induced by the levee system produced a steeper water surface slope in the downstream channel, causing a high-rate discharge to Tokyo Bay, where the water level was practically constant. These results suggest that the river engineering of Japan in the seventeenth century was based on a levee design technique with the aim not of restraining floodwaters with levees but of generating water head differences to divert flood flow from urban areas.

NUMERICAL STUDY ON THE CAPABILITY OF HYAKKEN-GAWA FLOODWAY IN EDO PERIOD

This paper presents a set of numerical flow simulations to investigate the flood control capacity of the Hyakken-gawa which was constructed as a floodway of the Asahi River for preventing inundation of Okayama Castle City in the 17th century. The river channel topography and hydraulic conditions for calculation were assumed almost same as the previous study, but the inundation to the eastside alluvial plain was calculated together to estimate its effect on the reduction of food damage in the castle city. The numerical simulation showed that the backwater caused by the transverse dikes in the floodway induced the inundation to the eastside plain just before the inundation would start in the castle city. The result suggests that the flood control planning in the age took the inundation to the eastside plain into account at the time of unusual flood events.

INVERSE ESTIMATION OF RIVER DISCHARGE HYDROGRAPH IN OPEN-CHANNELS WITH FLOOD PLAINS BY USING ADJOINT SHALLOW-WATER MODEL

This study proposes the methodology on an inverse estimation of a flood discharge hydrograph in open-channels with flood plains. The hydrograph is iteratively identified by an adjoint shallow-water model with the hydraulic observation data. The proposed method was applied to the flood flow in a 20km-long lower reach of the Tone River, which occurred in mid-September, 1998. The verification data is the flow field which is obtained by analyzing the aerial photos taken during the flood. The assimilated data consists of the time-series of the water level gained at observation stations within the domain. The results showed that the observed hydrograph is improved reasonably by the proposed method.

Practical techniques for measurement and analysis of fluctuating components in large scale hydraulic model test in open air --- A case study of cut-off channel flow---

This paper discusses practical techniques to measure fluctuation of velocity as well as of water surface level in a large scale hydraulic model test which is often carried out in open air. 1/70 scale model of a cutoff channel of actual river was used for the purpose. PIV measurement by using a fine resolution digital camera with short interval shooting was adopted for continuous velocity measurement in a wide area. A set of six servo level gauges was used for time series measurement of water level on each transect line. The data sets obtained separately by the methods mentioned above were synchronized by referring to a time series of water level measured at a fixed station. Correlation analysis of the synchronized data clarified the coherency of periodic fluctuation in time and space, and practical efficiency of the method was verified.

Quasi-3D Solver of Meandering River Flows by CIP-Soroban Scheme in Cylindrical Coordinates with Support of Boundary Fitted Coordinate Method

A new numerical solver is developed for the quasi-3D flow model to simulate meandering river flows. This solver can investigate the flows in an arbitrary curved river channel, by means of the adaptive CIP-Soroban (CIP-S) scheme in a cylindrical coordinate system with support of a boundary fitted coordinate (BFC) system. Time development of water velocity in an advection phase is computed by the orthogonal curvilinear coordinate system without any transformation of the governing equations, whereas a non-advection phase such as the continuity equation is solved by the BFC method, so that the mass conservation is fully satisfied and the water level is accurately calculated. From the verification of this solver on the meandering virtual river flows compared with the original BFC method, it is shown that the proposed solver accurately predicts the main flow profile in the regularly curved section of the flows, and that the horizontal velocity vectors both at the free-surface and at the bottom are reasonably predicted with the effect of the secondary currents in the curved section of the virtual river with some tributary streams.