Operational impact-based flood forecasting in data-scarce environments: the Early Warning System of the Buzi watershed in Mozambique&#160;
Authors: Libertino Andrea , Masoero Alessandro , Poletti Maria Laura , Filimone Isac , Darienzo Matteo , Pignone Flavio , Fagugli Giacomo , Romano Lia , Vilanculos Agostinho , Rossi Lauro , Gabellani Simone 
Published: March 2022

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&lt;p&gt;&lt;span&gt;Mozambique is one of the countries in Africa most frequently and most seriously affected by natural disasters such as floods, cyclones and droughts.&amp;#160;In&amp;#160;March&amp;#160;2019 the Cyclone&amp;#160;Idai, one of the Southern Hemisphere&amp;#8217;s deadliest storms, made landfall in the central part of the country, affecting about 1.7 million citizens, with&amp;#160;devastating&amp;#160;flooding in the central part of the country, especially in the Buzi and Pungwe river basins.&amp;#160;Despite the existence of several studies aimed at the hydrological characterization of the area, the unexpected severity of the event&amp;#160;undermined the&amp;#160;local EW/EA system.&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;&lt;span&gt;In the framework of the ECHO funded project &amp;#8220;&lt;/span&gt;&lt;em&gt;&lt;span&gt;Building inclusive resilient communities and schools to face rapid-onset hazards in risk-prone areas in Mozambique affected by cyclone&amp;#160;Idai, linking early warning to early action&lt;/span&gt;&lt;/em&gt;&lt;span&gt;&amp;#8221;,&amp;#160;an operational flood forecasting system,&amp;#160;up to&amp;#160;real-time inundation mapping,&amp;#160;have been implemented for the Buzi watershed&amp;#160;(30&amp;#8217;000 km&lt;/span&gt;&lt;span&gt;2&lt;/span&gt;&lt;span&gt;, in&amp;#160;Manica&amp;#160;and&amp;#160;Sofala&amp;#160;Provinces),&amp;#160;with the aim of increasing the&amp;#160;preparedness and response capacity to rapid onset disasters of the local and national levels of the EW/EA systems.&amp;#160;For granting the sustainability and the maintenance of the tool, the operational chain has been implemented in co-operation with the local authorities&amp;#160;(DNGRH)&amp;#160;and is based on the use of open-source free&amp;#160;software and models.&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;&lt;span&gt;A preliminary collection of the available data has been carried out for the setup and the calibration of the&amp;#160;CONTINUUM&amp;#160;hydrological fully distributed model (Silvestro, 2013). Several existing studies have been considered for the development of the land data and the collection of hydrological measurements for calibration.&amp;#160;Furthermore, the&amp;#160;outdated&amp;#160;level-discharge rating curves available have been reviewed and updated&amp;#160;using an innovative approach&amp;#160;(BayDERS,&amp;#160;Darienzo&amp;#160;2021).&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;&lt;span&gt;Stemming from the output of a long-term hydrological simulation&amp;#160;fed with meteorological reanalysis&amp;#160;conditioned with local rainfall data,&amp;#160;dynamic flood scenarios have been developed&amp;#160;for the&amp;#160;Dombe&amp;#160;flood prone community&amp;#160;by setting up&amp;#160;a&amp;#160;hydraulic model with the Telemac-2D&amp;#160;open system&amp;#160;using&amp;#160;the&amp;#160;Copernicus&amp;#160;DSM&amp;#160;at&amp;#160;30&amp;#160;m resolution&amp;#160;as&amp;#160;topographical input.&amp;#160;Outcomes&amp;#160;obtained&amp;#160;by simulating the&amp;#160;Idai&amp;#160;2019 flood&amp;#160;has been compared&amp;#160;with satellite images,&amp;#160;demonstrating&amp;#160;good agreement and&amp;#160;reliability of the implemented model.&amp;#160;Modelled flood maps have been shared&amp;#160;and commented&amp;#160;with the local community&amp;#160;in&amp;#160;Dombe,&amp;#160;with the dual objective of receiving feedback&amp;#160;on&amp;#160;map reliability and&amp;#160;increasing&amp;#160;flood risk&amp;#160;awareness.&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;&lt;span&gt;The full&amp;#160;flood forecasting&amp;#160;chain&amp;#160;for the Buzi watershed&amp;#160;has been then operationally implemented by means of the&amp;#160;FloodPROOFS&amp;#160;open-source&amp;#160;modelling system (&lt;/span&gt;&lt;span&gt;https://github.com/c-hydro&lt;/span&gt;&lt;span&gt;),&amp;#160;fed&amp;#160;twice&amp;#160;per day&amp;#160;by&amp;#160;deterministic&amp;#160;and probabilistic&amp;#160;forecasts&amp;#160;freely provided by NOAA (GFS and GEFS).&amp;#160;Operational forecasts&amp;#160;are made available to DNGRH officers through the&amp;#160;myDEWETRA.world&amp;#160;EW platform,&amp;#160;informing&amp;#160;on&amp;#160;potential flood&amp;#160;events&amp;#160;expected for the following 5 days,&amp;#160;including&amp;#160;their probability of occurrence,&amp;#160;thus&amp;#160;facilitating&amp;#160;decision&amp;#160;making&amp;#160;in&amp;#160;issuing early warnings and&amp;#160;taking&amp;#160;early action measures.&lt;/span&gt;&lt;/p&gt;
&lt;p&gt;&lt;span&gt;Finally, for the&amp;#160;Dombe&amp;#160;pilot-case&amp;#160;the&amp;#160;flood depth and water velocity maps are combined with the spatial distribution of the exposed assets, identified in collaboration with the&amp;#160;community itself,&amp;#160;resulting in&amp;#160;real-time forecasts of the expected impacts.&lt;/span&gt;&lt;span&gt;&amp;#160;&lt;/span&gt;&lt;/p&gt;
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