Public Works Research Institute

Abstract This study evaluates the valorization of grape stalks (GS) and winery waste activated sludge (WWAS) via mesophilic co-composting to produce high-quality soil amendments. The primary objective was to resolve uncertainties regarding the necessity of a thermophilic phase for these residues and to identify the optimal operational parameters for effective stabilization. Composting performance was assessed through laboratory-scale trials (12–42 °C) and a nine-week pilot-scale experiment conducted under ambient conditions. The results demonstrate that effective stabilization and organic matter degradation are achievable without a thermophilic phase, provided moisture levels are maintained between 55 and 75%. Microbial activity was found to be highly moisture-dependent, with significant performance declines observed when moisture dropped below 40%. The final composts exhibited superior agronomic quality, characterized by low phytotoxicity (Germination Index > 90%), rapid odor neutralization, and enhanced carbon retention (C:N ratio of 23.8 in pilot trials), suggesting lower greenhouse gas emissions compared to traditional thermophilic processes. These findings establish mesophilic co-composting as a technically viable, low-energy, and scalable strategy. By maximizing carbon fixation and simplifying infrastructure requirements, this approach offers a cost-effective solution for transforming underutilized winery by-products into safe, stable organic fertilizers, directly supporting circular economy goals in viticulture. Graphical Abstract

Tropical lakes such as Lake Sentarum in Kalimantan, Indonesia, represent ecologically rich ecosystems with high biodiversity and constitute the largest lake on the island of Kalimantan. This lake serves as a sensitive indicator of climate change; however, its monitoring is often hindered by persistent cloud cover. This study evaluates the effectiveness of a Gradient Tree Boosting machine learning model integrated with multisource satellite data, including optical imagery, Sentinel-1 SAR, Sentinel-2, and high resolution NICFI data, in accurately mapping surface water dynamics. The Gradient Tree Boosting model was trained and validated using water and non water samples collected from annual imagery spanning 2019 to 2024, achieving validation accuracies ranging from 80 percent to 97 percent. Results demonstrate that Gradient Tree Boosting successfully integrates the strengths of each sensor, producing consistent annual water maps despite extreme hydrological fluctuations caused by El Niño and La Niña events. These findings highlight the model's potential application in water resource management, particularly in providing accurate baseline data to support adaptation planning for droughts and floods in climate vulnerable regions. • Utilized optical and radar remote sensing data for accurate spatiotemporal monitoring of seasonal and interannual changes in water extent. • Gradient Tree Boosting model to classify water and non-water areas with high accuracy. • Integrated Google Earth Engine for efficient cloud-based processing and time-series analysis of large geospatial datasets. • Provided insights into climate-driven hydrological patterns to support sustainable water resource management in tropical lake.

Understanding urbanization and its impact on flooding and flood risk is crucial to better manage flood risk in the future. This study analyzed land use/land cover changes and how urbanization would impact flooding and flood risk in Kathmandu Valley of Nepal, and assessed flood risk by integrating flood hazards based on hydrologic–hydraulic modeling with the Analytic Hierarchy Process-based Multi-Criteria Decision Analysis (AHP-MCDA) approach. Land cover maps for past years were generated using Landsat satellite images, and land use/land cover maps for future years were projected based on machine learning techniques. Flood simulations were conducted using a rainfall runoff inundation model with land cover maps for different flood scales to analyze the impact of urbanization and land cover changes on flood runoff, flood inundation extent, and flood inundation volume. Then, we comprehensively assessed flood risk by integrating hazard conditions simulated under different land cover conditions using a hydrologic–hydraulic model and the AHP-MCDA approach. The results showed that the flood inundation extent and the peak inundation volume for a 200-year flood may increase in the future by 10.66% and 15.04%, respectively, as a result of urbanization. The results also highlighted that urbanization may lead to an expansion of high-risk and very-high-risk areas in the future by 3.2% and 9.4%, respectively, indicating an increase in the valley’s flood vulnerability and greater severity of flood hazards.

Seismic hydrodynamic pressure, which is a burst water pressure fluctuation induced by earthquakes, is often observed in water pipelines. The earthquake damage includes detachment and damage to pneumatic valves in curved pipe sections, and we believe that the fluctuation of internal water pressure during earthquakes may have an effect on these phenomena. Since there have been a few cases of actual measurements of seismic hydrodynamic pressure on pipelines, it has not been fully reflected in the design of agricultural pipelines and earthquake countermeasures at this time. In this study, we attempted to evaluate the relationship between acceleration and water pressure fluctuation by frequency analysis using FFT for the measured seismic hydrodynamic pressure in an agricultural pipeline.

Abstract The present study describes a river channel management method for restoring riverine environments degraded by sand mining in rivers. Specifically, three conditions that must be met for a restored river channel in the lower reach of the Kelani River in Sri Lanka were proposed: (1) flood discharge capacity of the channel for a given flood, (2) prevention of saltwater intrusion, and (3) creation of a diverse physical environment. The allowable mining volume satisfies the three conditions, while continuing to mine sand was discussed based on the sediment budget calculations in the target river reach. In this case, the amount of sediment stored in the target reach and its variation are determined by the amount of sediment supplied to the target reach, the amount of sediment discharged from the target reach to the sea, and the amount of sediment excavated. This means that the dynamic equilibrium channel of the target reach is determined by the amount of sediment supplied and the amount of sediment excavated. The amount of sand mined when the dynamic equilibrium channel meets the three conditions of the restored channel is a candidate for the allowable amount of sand mined. One of these, the most desirable one, is set as the allowable mining volume. As described above, we proposed a method to develop a restoring reach taking the sediment budget and associated hydraulic and hydro morphological conditions in the target reach into consideration.

The extent of alien taxa impacts on river ecosystem health is unclear, but their frequency continues to rise. We investigated 1) the prevalence of including alien taxa in common bioindicators used in river bioassessment, 2) the effect of alien taxa on the richness and abundance of natives, and 3) whether including alien taxa in bioassessment tools increased their sensitivity to river degradation. In the 17 countries analyzed fish represented the greatest number of alien species (1726), followed by macrophytes (925), macroinvertebrates (556), and diatoms (7). Yet, alien species are only distinguished from natives in some fish and macrophyte indices. In addition, the analyses of 8 databases with fish, macroinvertebrate, or macrophyte data showed that abundance of alien taxa was associated with different stressors and pressures resulting in river degradation, and had a significant effect on native community composition. When alien species were accounted for, there was a strong negative correlation between the values of a fish index with alien richness and abundance while when alien taxa was not or only partially considered the results varied. Thus, we recommend: 1) Include specific metrics for alien species in biological quality indices. 2) Increase the investigation of alien taxa of small organisms (e.g. diatoms, small benthic invertebrates). 3) Eliminate sites with confirmed biological invasions for use as reference sites. 4) Remove alien from calculations of total richness and diversity. 5) Identify to the species level in biomonitoring programs. 6) Avoid legislation and management that protect alien species. 7) Encourage behaviors that prevent alien invasions of aquatic biota.

This study investigated the physical properties of hardened cement incorporating biomass ash (BA), considering the effect of the ratio of nonbridging oxygen atoms to tetrahedral-forming ions (NBO/T), a chemical indicator of ash. The reactivity of fly ash (FA) exhibited strong positive correlation with NBO/T, which can also serve as a reactivity indicator for other supplementary cementitious materials like slag. Chemical analysis revealed that BA possesses properties of both FA and blast furnace slag. During curing, the number of voids corresponding to small and large gel pores, formed by coagulated C–S–H, increased significantly, with sizes reaching tens of nanometers. Fourier transform infrared and aluminum nuclear magnetic resonance analyses showed that cement incorporating BA had higher compressive strength than coal ash-based cement, with higher contents of ettringite, C–A–S–H, and monosulfate after 28 days. This was attributed to the distinct compositions of coal and BA, alongside the usage of seawater and gypsum. Moreover, BA further enhanced the compressive strength owing to the influence of hydration products, including C–S–H. This positive correlation between NBO/T of BA and the compressive strength of the cured material suggests that NBO/T can serve as an indicator for estimating cement blending strength.

Present study examines responses of the longitudinal bed profiles to bed shear stress changes and associated changes of the bed load transport rates which are caused in straight open channels with different flow widths where the channel is connected by an abruptly widened approach or a narrowed one. To investigate the response of bed slope ratio to the change of bed-load transport rate, we employ two bed load formulas for discussions; one is the bed- load formula characterized by τ∗3/2 with τ∗c, and the other is the bed load formula expressed by τ∗5/2. Besides, to see role of the bed load formula explicitly in the regime relation, the regime formulas for describing the bed slope ratio, specific bed elevation etc. were obtained, assuming that an equilibrium sediment transportation accomplished. The regime formula shows that the bed slope ratio, i2/i1 increases monotonically with the increase of the flow width ratio when τ∗5/2 type of the bed load formula is employed in the regime equation, where suffixes 1 and 2 show the quantities upstream and downstream. However, the regime formula shows that the bed slope ratio depends on the bed shear stress change when τ∗3/2 type bed load formula is employed. The present study topics are classic, and not new, but it is very important to study the response of the longitudinal bed profile to the bed load transport rate to look for a suitable form of the bed load equation.

Following an earthquake, roads must be opened as soon as possible for emergency transportation. Therefore, the damages to road bridges must be quickly and accurately assessed and their structural safety and serviceability must be confirmed. For this purpose, current post‐earthquake inspections are first conducted by vehicle patrols, followed by hands‐on inspections in case of irregularities on the road surface. However, this inspection method is time‐consuming. Despite this, in post‐earthquake inspections, the safety of structures must be accurately diagnosed and fatal damages must not be overlooked. Therefore, inspection methods must be highly reliable. To clarify the scope of application where the quality of inspection results is guaranteed, this study examined the correspondence between measurement conditions and quality and proposed a concept for evaluating this relationship. Based on this concept, we present a method to evaluate the extent of damage based on images captured by unmanned aerial vehicles (UAVs) that are utilized for post‐earthquake inspections. Experiments were conducted to verify the deformation detection accuracy of UAVs. The results indicated that at a distance of 2 m, cracks ≥ 0.3 mm, deformation angles ≥ 1°, and movements ≥ 2 mm can be confirmed. This conformity evaluation, which was also confirmed by cross‐checking with the actual damages, demonstrates the potential of this technology for practical applications.