Many studies have shown a growing trend in terms of frequency and severity of extreme events. As never before, having tools capable to monitor the amount of rain that reaches the Earth’s surface has become a key point for the identification of areas potentially affected by floods. In order to guarantee an almost global spatial coverage, NASA Global Precipitation Measurement (GPM) IMERG products proved to be the most appropriate source of information for precipitation retrievement by satellite. This study is aimed at defining the IMERG accuracy in representing extreme rainfall events for varying time aggregation intervals. This is performed by comparing the IMERG data with the rain gauge ones. The outcomes demonstrate that precipitation satellite data guarantee good results when the rainfall aggregation interval is equal to or greater than 12 h. More specifically, a 24-h aggregation interval ensures a probability of detection (defined as the number of hits divided by the total number of observed events) greater than 80%. The outcomes of this analysis supported the development of the updated version of the ITHACA Extreme Rainfall Detection System (ERDS: erds.ithacaweb.org). This system is now able to provide near real-time alerts about extreme rainfall events using a threshold methodology based on the mean annual precipitation.

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A protocol for assessing the quality of digital geospatial data is applied to samples of volunteered geographic information (created by Humanitarian OpenStreetMap Team) and professional mappers (Copernicus EMS-rapid mapping). The application on pre-event data shows that a large percentage of them is very similar in terms of quality and is, therefore, potentially interchangeable; post-event data reveal a more divergent behaviour. The results gathered from the comparative analysis and a look at the temporal trends of response of volunteers and professionals justify a framework of interaction of respective activities, which seems to be possible under strong relationship between professionals and volunteers, built upon common operational standards and guidelines.

This paper presents a methodology aimed at enabling local government personnel and decision makers to easily process satellite-derived precipitation data for the assessment of extreme precipitation hazard and to integrate them with geospatial reference datasets for the production of timely and meaningful flood risk information, considering also the assessment of exposed infrastructure, population or assets. The methodology relies on the use of the Malawi Spatial Data Platform (MASDAP), a GeoNode web platform for the management and publication of geospatial data, developed in the framework of the Shire River Basin Management Program (SRBMP). The proposed work-flow has been illustrated during a capacity building training held in Blantyre (Malawi) in December 2015 and constitutes a standardizable decision support approach, particularly useful for countries where meteo-hydrological observations are scarce or have a too coarse resolution.

ABSTRACT:Several studies have been conducted in Africa to assist local governments in addressing the risk situation related to natural hazards. Geospatial data containing information on vulnerability, impacts, climate change, disaster risk reduction is usually part of the output of such studies and is valuable to national and international organizations to reduce the risks and mitigate the impacts of disasters. Nevertheless this data isn't efficiently widely distributed and often resides in remote storage solutions hardly reachable. Spatial Data Infrastructures are technical solutions capable to solve this issue, by storing geospatial data and making them widely available through the internet. Among these solutions, GeoNode, an open source online platform for geospatial data sharing, has been developed in recent years. GeoNode is a platform for the management and publication of geospatial data. It brings together mature and stable open-source software projects under a consistent and easy-to-use interface allowing users, with little training, to quickly and easily share data and create interactive maps. GeoNode data management tools allow for integrated creation of data, metadata, and map visualizations. Each dataset in the system can be shared publicly or restricted to allow access to only specific users. Social features like user profiles and commenting and rating systems allow for the development of communities around each platform to facilitate the use, management, and quality control of the data the GeoNode instance contains (geonode.org). This paper presents a case study scenario of setting up a Web platform based on GeoNode. It is a public platform called MASDAP and promoted by the Government of Malawi in order to support development of the country and build resilience against natural disasters. A substantial amount of geospatial data has already been collected about hydrogeological risk, as well as several otherdisasters related information. Moreover this platform will help to ensure that the data created by a number of past or ongoing projects is maintained and that this information remains accessible and useful. An Integrated Flood Risk Management Plan for a river basin has already been included in the platform and other data from future disaster risk management projects will be added as well.