Slapis Sahel Archives - climateservices.it CNR-IBE

Linking Earth Observation and Precipitation In-Situ Data in the Sirba River Basin in West Africa

Vieri Tarchiani — Tue, 30 Jun 2026 09:50:54 +0000

Floods have caused substantial loss of life and economic damages in West Africa, with a marked increase of extremes over the past decades. These flood events are largely driven by frequent extreme local rainfall. The sparse meteorological stations in Burkina Faso contain data gaps that limit effective monitoring of rainfall. This study fills the gap by integrating satellite data with in-situ precipitation measurements. This study assesses spatio-temporal correlations between cloud coverage and reservoir surface water areas extracted from Sentinel-2 to in-situ rainfall historical data complemented with spatially explicit gridded meteorological products, including ERA5 and CHIRPS. In-situ precipitation shows a strong correlation with cloud coverage (Mean r = 0.65), better agreements with ERA5 (r = 0.83) and CHIRPS (r = 0.91), and a timelagged correlation with surface water areas. A developed open-access app (Abraiz, 2026) provides insights for realtime dynamics of the cloud coverage, precipitation, and surface water area of reservoirs in the Sirba River basin with potential applicability in other data-scarce regions.

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A streamlined flood-specific evaluation framework: Assessing African riverine early warning systems

Vieri Tarchiani — Fri, 26 Jun 2026 08:38:28 +0000

Intense hydrological events are rising across Africa, increasing flood risks. Flood Early Warning Systems (FEWS) are internationally acknowledged as fundamental tools for risk reduction and management. Their effectiveness depends on the integrated and balanced development of all essential components -risk knowledge, monitoring and forecasting, dissemination and communication, preparedness and response-yet their integration across operational systems is poorly documented.

This study develops a flood-specific evaluation framework adapted from the UNDRR-WMO Multi-Hazard Early Warning System Custom Indicators (MHEWS-CI), reducing its 53 indicators to 25 through thematic consolidation and flood-specific adaptation. The framework is applied to assess 19 African riverine FEWS using publicly available documentation, as a proof-of-concept. Each indicator is assessed through a recognition-based approach: documented system functionalities are matched against three predefined development stages (absent, basic, advanced), lightning the reporting burden of MHEWS-CI. Scores are compared to illustrate relationships between system characteristics and development of components.

Results reveal imbalances: 74% of systems demonstrate advanced monitoring and forecasting, but only 5% achieve advanced response capabilities. Web architectures and hydrological models favour monitoring and forecasting but show no corresponding advantage in response integration. Hybrid systems combining model forecasting with community engagement achieve the highest overall scores, suggesting that optimal development requires balancing technical sophistication with a participatory approach.

These patterns may reflect institutional factors -governance fragmentation and insufficient operational integration-rather than causal effects of system characteristics. The framework delivers a streamlined, replicable instrument for insightful FEWS assessment, successfully corroborating prior research and supporting evidence-based identification of operational gaps and investment prioritisation.

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Dataset on Flood Risk Along the Niger River Upstream of Niamey

Vieri Tarchiani — Wed, 10 Jun 2026 14:31:38 +0000

Knowledge of river flood risk in semiarid rural areas is often based on outdated, low-resolution geoinformation. Consequently, identification of exposed settlements, assets and risk-reduction measures remains challenging. This dataset provides up-to-date, fine-grained information for a rural area spanning 931 km² that is exposed to flooding from the Niger River and the Karma Wadi. The dataset includes information on (i) areas exposed to the two flood types that characterise the river’s hydrological regime and flash floods from the wadi, (ii) flood-prone crops, buildings and (iii) measures for risk treatment. Discharge data, a 4 m horizontal-resolution digital elevation model, and two-dimensional hydraulic modelling with BASEMENT were used to identify flood-prone areas. Visual interpretation of high-resolution satellite imagery in Google Earth, together with field inspections, enabled the identification of exposed assets. The Information System on Rural Markets of Niger and house compensation values recognised during resettlement-related works enabled asset valuation. Risk was expressed in monetary terms as the product of flood probability and expected damage. Risk-reduction measures were identified with stakeholders through a SWOT analysis and prioritised using eight criteria. The dataset can support emergency plans, flood early warning systems, rescue and recovery operations and flood risk management.

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Mapping precipitation extremes for pluvial flood risk management in the Sirba river basin, Burkina Faso

Vieri Tarchiani — Fri, 22 May 2026 10:11:30 +0000

Sahelian Africa is increasingly exposed to extreme hydrological events. Both fluvial and pluvial floods are becoming more severe and frequent, posing significant new threats to the livelihoods of local communities. To enhance resilience to floods, the development of effective operational tools for assessing risk and supporting decision-making is crucial. When it comes to pluvial floods, the first step towards this goal is to improve the understanding of extreme daily and sub-daily precipitation events and their spatial patterns in the target areas. Within the SLAPIS Project framework, this work does so for the Sirba river basin (Burkina Faso and Niger) proposing a methodology to address the challenges posed by the scarcity of hydrological data typical of the Sahel region. First, it was assessed how well gridded precipitation products (ERA5, TRMM, TAMSAT) match observed rainfall records. Then, bias correction of selected datasets was performed and tested to evaluate its reliability when spatially interpolated through the whole basin. The Metastatistical Extreme Value Distribution was finally applied to the corrected datasets to investigate the precipitation extremes exploiting the bulk of the available data, unlike classical extreme value analysis, which relies on only a small subset of the data. This procedure resulted in the production of extreme daily and sub-daily precipitation maps with enhanced accuracy and robustness, providing novel information on events that can cause pluvial flooding at the settlement scale. The methodology adopted in this study could be applied to other Sahelian basins where enhanced knowledge of extreme precipitation magnitudes and patterns is needed.

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From training to transformation: co-producing sustainable early warning competence in West Africa

Vieri Tarchiani — Mon, 13 Apr 2026 09:51:45 +0000

Operational numerical weather prediction in Sub-Saharan Africa remains fragile despite increasing availability of models and data. A key limiting factor is the limited operational and institutional capacity of National Meteorological Services to operate, assess, adapt, and sustain forecasting chains within routine operations for early warning systems. Short-term, tool-oriented training initiatives often fail to address this gap, as learning remains weakly embedded in daily service delivery and rarely translates into sustained operational competence.

This paper presents a qualitative case study examining how co-production principles can be operationalized to support the development of operational competence for flood early warning. The study draws on a long-term capacity-development experience involving the National Meteorological Services of Niger and Burkina Faso and the Tuscany Regional Meteorological Service in Italy. The approach combined long-term embedding of trainees within an operational forecasting team, training-of-trainers, and peer-to-peer institutional collaboration, linking learning to real operational workflows.

Results are analysed across methodological, operational, and institutional dimensions. Methodological findings show how co-production principles can structure competence-oriented training processes by integrating instructional design, operational practice, and iterative evaluation. Operational results highlight the importance of sustained practice and routine verification, while institutional results point to the role of training of trainers and public institutional collaboration supporting sustainability of competence beyond individual skills and knowledge.

By reframing competence as a foundational component of climate services, the study offers transferable insights for capacity development in resource-constrained and transboundary contexts.

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DEM Generation from Multi-View Satellite Images in Sub-Sahel Region

Web Editor — Fri, 13 Jun 2025 07:37:12 +0000

Floods are causing a significant loss of human lives and valuable resources in West Africa. In particular, Niger and Burkina Faso were highly affected areas in past years. In order to predict flood, an accurate Digital elevation model (DEM) is required for flood mapping. At the studied area in Niger, up to this date, the LiDAR DEMs are scarcely available, and the only available DEMs are global DEMs like global SRTM DEMs with a resolution of 10m. These global DEMs are not accurate enough to be used for flood mapping. So, in this context, this study investigates the potential of multidate, multi-view stereo pairs PlanetScope images for the generation of DEM. Three DEMs were generated from images with slightly different view angles to see the effect of view angles of images on 3D modelling. One of the DEM generated by PlanetScope images was compared with DEM generated by high-resolution drone imagery and shows the normalized Median of Absolute Deviation (NMAD) of the elevation differences of 10m. Results show that planetScope images are useful assets for generating multiple DEMs due to their high temporal resolution. Such DEMs could be extremely useful for studying dynamic phenomena or monitoring disaster events like floods.

Keywords: Remote Sensing, DEM Generation, Cubesat Satellites, Stereo-Modelling, 3D Modelling

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Bridging the communication gap in agrometeorological services: Enhancing the uptake and effectiveness for users in developing countries

Web Editor — Wed, 04 Jun 2025 14:50:50 +0000

Over the past decades, advancements in agrometeorological monitoring and forecasting have been driven by technology, infrastructure, and capacity building. Literature highlights that agrometeorological services support agricultural decision-making, boosting farmers’ resilience and income globally. However, challenges in communication and dissemination limit their effectiveness, particularly for smallholder farmers in remote areas. The problem extends beyond media type and format to issues of accessibility, comprehensibility, and users’ trust. While technology has enabled faster dissemination, there is a risk of new services being technology-centered rather than user-focused. This non-systematic literature review delves into effective communication strategies for agrometeorological information in developing countries, reviewing existing knowledge and presenting case studies. It addresses how to ensure access to information, identify efficient communication channels, use inclusive technologies, enhance users’ understanding, make information actionable, and gather feedback on information effectiveness. Stakeholders’ engagement methods include a variety of participatory approaches and iterative monitoring, evaluation and learning processes. The choice of communication channels significantly affects information reach. Despite the rise of ICT, challenges in access and understanding persist, especially for marginalized groups, making simple communication technologies like rural radios still crucial for last-mile dissemination. The review emphasizes that no single communication approach fits all situations. Key principles of coproduction and user engagement in climate services are essential for effective agrometeorological communication. Future directions include enhancing the legitimacy and salience of services by integrating local knowledge, expanding scope to include herders and off-farm stakeholders, building capacity among intermediaries and users, soliciting feedback, and fostering public–private partnerships for scaling and sustainability.

Keywords: Agricultural Meteorology; Communication; Climate Services; Co-production; Stakeholders engagement; Best practices

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Flood risk assessment of agricultural areas along the Niger river upstream Niamey

Web Editor — Wed, 30 Apr 2025 13:24:37 +0000

Much of the food supplied to the city of Niamey (1.5 million inhabitants), the capital of Niger, comes from 150 large commercial horticultural sites and 10 vast irrigated perimeters distributed along the Niger River upstream of the city. These areas are threatened by floods, such as the one that devastated paddy fields and horticultural areas in August 2024. To address this problem, a detailed assessment of the river flood risk, expressed in monetary terms, is urgently needed to complement the early flood warning system.

This activity is part of the SLAPIS Sahel project, which aims to develop a more general framework for flood risk management applied to the transboundary Sirba river basin and the nearby Niger river, with the active participation of the water authorities of Burkina Faso and Niger. In this context, this work focuses on the flood risk analysis of the Niger River upstream of the city of Niamey in a multidisciplinary way. To this aim, a hydrological study of the basin was carried out, taking into account the two types of floods that affect the area: floods due to the local rainy season, and dry season events caused by floods upstream in the Guinea-Conakry basin. A hydraulic model was then used to map the extent of flooding, allowing to study the impact and expected damage to the target areas. Daily satellite imagery was used to assess the extent of recent floods and the characteristics of the exposed areas. All these activities were repeated for both the wet and dry seasons, as agricultural production changes and the impacts are different.

This analysis supports the cost-benefit assessment of possible defense structures.

Link to EGU presentation EGU25_PICO_SLAPIS

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Flood Damage Risk Mapping Along the River Niger: Ten Benefits of a Participated Approach

Web Editor — Wed, 30 Apr 2025 13:17:14 +0000

Flood risk mapping is spreading in the Global South due to the availability of high-resolution/high-frequency satellite imagery, volunteered geographic information, and hydraulic models. However, these maps are increasingly generated without the participation of exposed communities, contrary to the Sendai Framework for Disaster Risk Reduction 2015–2030 priorities. As a result, the understanding of risk is limited. This study aims to map flood risk with citizen science complemented by hydrology, geomatics, and spatial planning. The Niger River floods of 2024–2025 on a 113 km2 area upstream of Niamey are investigated. The novelty of the work is the integration of local and technical knowledge in the micro-mapping of risk in a large area. We consider risk the product of a hazard and damage in monetary terms. Focus groups in flooded municipalities, interviews with irrigation perimeter managers, and statistical river flow and rainfall analysis identified the hazard. The flood plain was extracted from Sentinel-2 images using MNDWI and validated with ground control points. Six classes of assets were identified by visual photo interpretation of very high-resolution satellite imagery. Damage was ascertained through interviews with a sample of farmers. The floods of 2024–2025 may occur again in the next 12–19 years. Farmers cannot crop safer sites, raising significant environmental justice issues. Damage depends on the strength of the levees, the crop, and the season. From January to February, horticulture is at a higher risk. Flooding does not bring benefits. Risk maps highlight hot spots, are validated, and can be linked to observed flood levels.

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Compound-event analysis in non-stationary hydrological hazards: a case study of the Niger River in Niamey

Web Editor — Thu, 05 Dec 2024 12:49:56 +0000

This study examines compound hydrological hazards in a non-stationary context, specifically focusing on the Niger River in Niamey. The hazard results from the confluence of local Sahelian and more remote Guinean tributaries, displaying seasonal floods. The study first investigates whether Niamey’s annual flood hazard is a compound result of Sahelian and Guinean flows, and then assesses the value of a compound hazard approach versus traditional flood analyses in this region. Analyzing discharge data from 1950 to 2020, the study disentangles Sahelian and Guinean flow impacts. It compares flood return level estimations from three statistical models of varying complexity. Findings confirm Niamey’s hazard as compound, stressing the need to consider both tributaries separately. Incorporating non-stationarity in statistical modeling is crucial, yet fully integrating the compound nature of hazards doesn’t significantly change the quantitative estimation of the hazard in Niamey.

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