FLOODINGS against DESERTIFICATION

FLOODINGS against DESERTIFICATION

As I said in my previous post, water scarcity is responsible for the degradation of the environment, economy and society.

Usually, biologists assert that water is life. But I am not sure that Sierra Leone's population would agree with this statement. I plan to talk about the Sierra Leone case study in my next post to highlight this point.

Is water really life?

Source : Ked Youzhu

Improvment of pluviometric rates : consequence of floodings?

Despite the fact that African pluviometric rates are not at the same level as before the droughts in the 70's, it has been found that they have actually been recovering since the 90's (L.Descroix et al. , 2015).

As pluviometric rates are recovering, floodings have also been more frequently observed in Africa, especially in the western regions (P.OZET, D.PERRIN, 2014).

For instance, though the interior Delta of Niger had seen the flood plains disappear during the long period of droughts in the 70's - they have been recovering back to their initial level since the 90's (A.J. Beintema et al. ).

Just a simple figure that illustrates the increase of floodings from 1995

(P.OZET, D.PERRIN, 2014)

How can this pluviometric change be observed and understood ?

Climate characteristics transformations

Indeed, though the improvement of the rainy rates in Africa could generally be perceived as a good thing, it depends on the way that this increase is generated.

These floodings seem to be the result of changes to the climates characteristics. Three aspects of the African climate (particularly in the West) changed : rainy seasons, droughts, and extreme pluviometric events.

According to P.OZET, D.PERRIN, (2014), rainy seasons seem to be shorter (late establishment and early endings). The result of this can be really damaging not only due to its effects on agriculture, but also on groundwater uses which could not only be applied anymore to generate or promote water scarcity during dry seasons.

These two graphics are about rainy seasons during two different periods (a) 1951-1970 b) 1971 – 2000)

Source : Amani Michel Kouassi et al, 2010

IN ADDITION, this reduction to the rainy seasons duration is completed by its fragmentation with droughts (P.OZET, D.PERRIN, 2014). I will let you imagine impacts of this combination on agriculture, grazing, and the viability of water supply. It just makes water unpredictable and discontinued leading populations to find new ways to become adapted to the particular climate.

Climate change and previous droughts 

But these two aspects of West African climate are not the most important. Indeed, the significant change is the increase of extreme pluviometric events.

According to L.Descroix et al. 2015 an increase more pronounced is the occurrence of extreme rains translating to pluviometric rate gain.

These changes of characteristics to the African climate illustrate the role of the global climate change in this situation. However, this tranformation has been observed earlier in the dry regions (Sahel for instance).

Actually, it is asserted that climate changes have begun to affect Sahel from the last three decades while Guinean climate has shown transformations from these last ten years (P.OZET, D.PERRIN, 2014).

So it did not affect all the regions in the same way. Are urban and rural areas affected by floodings in the same way ?

Urban areas:

It is never simple in Africa, in truth, floodings seem to be more important in urban areas (P.OZET, D.PERRIN, 2014). 

Population growth: It couldn't be more correct as urban population is growing out of control. Therefore, a more important presence of humans on territories like cities generates bigger stakes. Indeed, the same rainfall does not affect the territory whether it includes inhabitants or not (P.OZET, D.PERRIN, 2014).

But, the demographic growth is not the only reason of the higher severity of floodings. They seem to have another origin, more political : A mismanagement of african territories is a leading cause of the flooding consequences.

Mismanaged land-use: According to P.Ozet et D.Perrin (2014), the recent flooding severity in Africa (particularly in the West) is the consequence of unsupervised dynamics of land uses in big cities.

Because of the rural-urban migration, partly due to the impoverishment of agricultural profitability caused by droughts, flows of populations move to cities in an uncontrolled way, building settlements wherever they can. And guess what ? It is often where nobody wants to live: in flood plain areas for example! Causing more damages to inhabitants, and worsening the consequence of floodings in these cities.

The district of Attecoube at Abidjan (Ivory Coast) in 2018, built on a flood area is often touched by floodings. In June, governments decided to move these inhabitants from high-risk areas.

Source : Le360 Afrique

However, cities are not the only places which are affected by floodings. Rural territories can also be damaged.

Rural Areas 

Indeed, in the same time, water scarcity generated by episods of droughts in the 70's drived rural populations to get closer to rivers (P.OZET, D.PERRIN, 2014). This migration made them now more vulnerable to the flooding events.

So, these two different areas are not affected in the same way but the consequences are still significant. It is asserted that unhealthy livestocks, reductions of the cereal yields, the increase of the frequency of the floods in certain cities, all degradating livelihood are attributed to climate change. (P.OZET, D.PERRIN, 2014)

But, we can detail this developing idea that series of doughts and rainy periods discontinuously are an important factor of the worsening of the situation.

Combination of droughts and rainy stages

Source: Agence France Presse

Because of the hortonian aspect of run-offs in this region (Particularly Sahel) and droughts observed fifty years ago (generating, I remind you, rural-urban migrations and move of rural populations next to the rivers) consequences of the increase of extreme rainy events have been multiplied the magnitude of floodings.

Indeed, according to L.Descroix et al. (2015) the degradation of soil and vegetation during doughts stages have completely limited the water-retention of soils, fields, watersheds and so on increasing the run-off.

For instance, we can mention the "Hydrological paradox of Sahel". During droughts an increase in run-off and consequently increase of flow. Vegetation cover decline or increase of temperatures have damaged the capacity of water retention creating an over abundance of water (L.Descroix, 2015).