Aftermath of Mathew hurricane over Haiti in 2016

Following Simon's publication on Saint Barthelemy island after Hurricane Irma, one of our twitter friends, @Pierre_Markuse, posted a comparison of the South Western part of Haiti, before and after Mathew huricane ravaged it last year, on the 4th of October 2016. As you can see, the whole lands turn brown just after the hurricane. I am really not an expert, so I just can imagine it is caused by the wind cutting branches and trunks and by water run-off taking the lower vegetation away.  I read that 40% or the  forest and 20% of the shrub has been erased. Moreover, the wind and water must have left mud and dust on the remaining leaves, contributing to the brown color.

 

However, what is amazing is that by end of November, vegetation comes back ! My guess is that mud and dust disappear, shrubs and trees start to grow new leaves and the low vegetation grows back  But experts are welcome to explain how it happens exactly, there is a comment section !

 

I have an additional special own interest in displaying this information :  it is a hard test for how our multi-temporal methods included in MAJA to detect clouds, shadows and aerosols can manage such a case. Continue reading

The Delta of the Ebro seen by Venμs

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The Delta of Ebro

Delta of the Ebro observed by Venμs on August 18, 2017 (Copyright CNES 2017)

The Ebro (Iberus in Latin) flows into the Mediterranean in Catalonia after a journey of more than 900 km from its source in Cantabria. The current morphology of the Delta results from the significant increase in sediment inputs caused in the 15th century by the intensive deforestation of the river catchment: the conquest of the Americas required the construction of boats. It was at this time that the land emerged over the sea, making the delta this wide plain of which only 10% of the land culminates at more than 2 meters. The construction since 1930 of 187 upstream dams reduces the sediment flow (from 28 Mt / year to about 0.1 Mt / year), which partly explains the erosion currently observed in some parts of the delta.

 

80% of the area of ​​the delta is devoted to crops, mostly rice producing one-third of the country's production. The rest, protected by the Natural Park, consists of lagoons, reed and rush beds,  brackish marshes and sandbanks.

 

The Delta de l'Ebre is included in one of the sites that will be observed by Venμs every two days for two and a half years. It is part of ClimaDat, a long-term climate research network. Different issues will be adressed: land use, phenology, greenhouse gas fluxes (CO2, CH4, N2O), vegetation productivity, role of saline inputs.

 

Complement: the evolution of the Ebro delta from the 4th century:

http://geographyfieldwork.com/EbroEvolution.htm

 

 

Le Delta de l'Ebre vu par Venµs

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Delta de l'Ebre

Delta de l'Ebre observé par Venµs le 18 août 2017 (Copyright CNES 2017)

L’Ebre (Iberus en latin) se jette dans la Méditerranée en Catalogne après un parcours de plus de 900 km depuis sa source en Cantabrie. La morphologie actuelle du Delta résulte de l'augmentation significative des apports de sédiments provoquée au XVe siècle par le déboisement intensif du bassin versant du fleuve : la conquête des Amériques nécessitait la construction de bateaux. C'est à cette époque que les terres émergées ont gagné sur la mer, faisant du delta cette large plaine dont seulement 10 % des terres culminent à plus de 2 mètres. La construction depuis 1930 de 187 barrages en amont réduit le flux de sédiments (de 28 Mt/an à 0,1 Mt/an environ), ce qui explique en partie l’érosion actuellement observée dans certaines parties du delta.

 

80 % de la superficie du delta sont consacrés aux cultures, en majorité de la riziculture qui produit le tiers de la production du pays. Le reste, protégé par le Parc naturel, est constitué de lagunes, roselières, jonchères, marais saumâtres et bancs de sable.

 

Le Delta de l’Ebre est inclus dans l’un des sites qui sera observé par Venµs tous les deux jours durant deux ans et demi. Il fait partie du réseau ClimaDat, un réseau de recherche à long terme sur le climat. Différents thèmes seront abordés : occupation du sol, phénologie, flux de gaz à effet de serre (CO2, CH4, N2O), productivité de la végétation, rôle des entrées salines.

 

Complément : l'évolution du delta de l'Ebre depuis le 4ème siècle :

http://geographyfieldwork.com/EbroEvolution.htm