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Hydrology

Volume XIV |

Flood exposure and settlement vulnerability in the Moldavian Plateau, Eastern Romania

Abstract: This paper quantifies settlement-level exposure to centennial flood across the Moldavian Plateau (NE Romania) using a reproducible GIS workflow. Official flood-hazard bands were intersected with built-up limits and building footprints; rural housing was completed by manual digitization, while urban fabric relied on OpenStreetMap layer. Exposed population was estimated from household counts using the national average of 2.6 persons/household, with additional rules for apartment blocks. Results are reported at multiple scales—by river basins (Siret, Jijia including Buhai–Miletin–Bahlui–Bahlueț, Bârlad and Prut/Chineja) and urban case studies (Iași, Bacău, Vaslui). The Siret basin concentrates the highest systemic exposure, Prut highlights transport-corridor vulnerability (DN/DJ roads and railway segments), while Bârlad exhibits dense, localized hot-spots. City-level estimates indicate approximately 68,750 exposed inhabitants in Iași, 36,756 in Bacău, and 2,550 in Vaslui under centennial flood scenario, together with clusters of socio-economic assets and critical infrastructure near the hazard band. Key limitations include potential under or over counts in recent developments, block-stairwell granularity, and reliance on census-based household averages. The findings support differentiated risk-reduction priorities: structural measures across Siret sub-basins, transport protection and redundancy along Prut, and targeted local actions in Bârlad. Periodic updates of hazard mapping using LiDAR and hydraulic modeling are recommended to refine exposure estimates and planning decisions.

Volume XXIII |

Tsunami evacuation modelling for region capacity evaluation in Panimbang, Pandeglang Regency, Indonesia

Abstract: Panimbang sub-district, located in the subduction zone of the Indo-Australian plate and directly facing Mount Anak Krakatau, is highly vulnerable to tsunami hazards. The region’s geographic location and its coastal topography make it particularly susceptible to the devastating impacts of tsunamis. This study assesses the region’s preparedness to manage tsunami risks using Geographic Information System (GIS) tools to model evacuation routes and estimate potential inundation areas. The research evaluates the effectiveness of the region’s evacuation capacity, considering critical factors such as population distribution, land cover, and the time required for residents to evacuate safely.
The study’s findings indicate that 74.91% of the 512.73 hectares of residential area in Panimbang is at significant risk of tsunami impact, potentially affecting approximately 38,723 people. This high level of exposure underscores the urgent need for tailored evacuation strategies, particularly in densely populated areas, to minimize the risk of casualties. The analysis also highlights the importance of enhancing infrastructure and disaster preparedness plans to increase the resilience of communities most vulnerable to tsunami threats. The research provides valuable insights into the critical elements of tsunami disaster management. It can serve as a crucial reference for future studies focused on improving evacuation routes, shelter planning, and other essential aspects of critical infrastructure. By addressing these areas, future efforts can more effectively safeguard the population in tsunami-prone regions, ensuring a more efficient and organized disaster response that significantly reduces the potential for loss of life and property.

Volume XXIII |

Modeling peak discharge on the Siret River (Romania)

Abstract: The purpose of this study is to identify potentially flood-prone areas in the section between the Siret hydrometric station and the confluence of the Siret River with the Suceava River.
Data related to water flow and specific flow parameters were incorporated into a dedicated hydrodynamic modeling program, in accordance with its requirements (DHI). The construction of the model focused on reproducing the field’s reality as faithfully as possible. Flow parameters were individually configured for each calculation section, taking into account their specific characteristics. Roughness values were determined non-uniformly based on the areas traversed by each cross-sectional profile.
Great emphasis was placed on model calibration, using monitored data from the Zvoriștea and Huțani hydrometric stations as reference points. A time series spanning 15 years, including two of the largest floods recorded in the sector, was used. Following the simulation of two scenarios, Q1% and Q0.1%, three types of files were generated, describing the flood boundary, water depth at each point on the boundary surface and water velocity at each point within the flood boundary. Localities and types of potentially flood-prone surfaces were identified on a map using GIS techniques. Furthermore, flood boundary limits from different scenarios were overlaid to quantify areas at risk of flooding. Although the scenarios were simulated on a previously calibrated model, the fact that the simulated flows exceeded the observed flows required several post-calibration steps. In the case of the first scenario, the simulation did not show significant errors, precisely because the Q1% flow is close in value to the maximum flows observed during the calibration period. In the case of the second scenario, the fact that the flow extended to non-specific areas even during historical maximum flows, resulted in stability errors or non-conforming results obtained by the program, inconsistent with research and studies in the field.

Volume XXIII |

Simulation of flood hazard in the semi-urban and urban using GIS and HEC-RAS of Wadi Nagues (Tebessa, North-Eastern Algeria)

Abstract: Floods are considered one of the most significant natural threats to cities and their infrastructure, especially when urban resilience is weak of floods, due to both human and natural factors. This is the case in the Algerian city of Tebessa, where urban resilience is low in the watershed of Wadi Nagues, which divides the city from north to south. Informal expansion along the riverbanks and inadequate city infrastructure increases the risk of flooding in the city. This study aims to identify the factors that increase flood hazards in Wadi Nagues and analyze maximum daily rainfall values to determine the maximum flood flow and volume during different return periods of 10, 50, 100, and 200 years, in order to map the floodplain of the river. This is accomplished using Geographic Information Systems (GIS) and HEC-RAS software for flood simulation. The results of the flood simulation in Wadi Nagues show that river waters inundate the southern areas of informal expansion, the airport, the railway, Houari Boumediene neighborhoods, and the Constantine Road – which is an economic artery for the city. The peak flow reaches 86.82 m³/h, and the volume of flow is 159.20 m³/s, in a during a 200-year return period. Field surveys also reveal several other human factors that increase the risk of flooding, such as informal expansion, lack and weakness of flood protection hydraulic structures, and poor river water cleanliness. This necessitates intervention to protect the city from flood hazard.

Volume XXIII |

Analysis of the seasonal and spatial variation of surface water quality parameters in Enugu Urban Rivers, Southeast, Nigeria

Abstract: Seasonal quality assessment of surface water provides not only a better understanding about pollution dynamics in water bodies but also information for the implementation of sustainable water-use management strategies. Such vital information is lacking for surface waters in most cities in sub-Sahara Africa region, especially Nigeria. The study aimed, therefore, to examine the seasonal physio-chemical characteristics of surface waters in Enugu urban, southeast Nigeria, during the dry and wet seasons. Twelve Surface water samples were collected from the six major rivers in Enugu urban during two seasons (wet and dry seasons). Their physico-chemical characteristics were determined by specific analyses between 2020 and 2022. Some of the parameters were measured in situ whereas bacterial analysis were analysed in the laboratory. Seasonal fluctuations in surface water quality characteristics were determined and the pollution status was compared to WHO standards. The results revealed that the parameters like Turbidity, Ammonia, Nitrate, Nitrogen, Fecal coliform and total coliform were above the WHO permissible limit at all sites and for all seasons. Various anthropogenic activities, untreated sewage and effluent were the major sources of pollution to the river ecology and the surface water. Overall monitoring network results must be used to control pollution in catchments where industrial and urban activities are increasing in other to ensure effective water quality management, sustainability and safety.