# Seasonal Floods, Terrestrial Biodiversity Survival Indices, and Local Population Resilience: Case Study of Koza in the Arid Sahelian Mountain Zone and Yagoua in the Arid Sahelian Plain Zone

Alexis Dzokom, Jules Balna, Etame Sone Diabe, Benjamine Anguessin

► To cite this version:

Alexis Dzokom, Jules Balna, Etame Sone Diabe, Benjamine Anguessin. Seasonal Floods, Terrestrial Biodiversity Survival Indices, and Local Population Resilience: Case Study of Koza in the Arid Sahelian Mountain Zone and Yagoua in the Arid Sahelian Plain Zone. Changements climatiques et les inondations dans le bassin du lac Tchad: Bien comprendre pour mieux gerer, Colloque International_Université de Maroua (Cameroun), Jun 2025, Maroua, Cameroon. pp.1-14. hal-05155026

HAL Id: hal-05155026

https://hal.science/hal-05155026v1

Submitted on 9 Jul 2025

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_1.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
<figure><img src="image_2.png" /></figure>

<figure><img src="image_3.png" /></figure>

Sahel Nature Consulting Revue

ISSN: 1401-0006

<figure><img src="image_4.png" /></figure>

<figure><img src="image_5.png" /></figure>

Protect Nature and People

<figure><img src="image_6.png" /></figure>

For Vulnerable Communities

<figure><img src="image_7.png" /></figure>

And Sustainable Energy, Agriculture and Ecology

# Seasonal Floods, Terrestrial Biodiversity Survival Indices, and Local Population Resilience: Case Study of Koza in the Arid Sahelian Mountain Zone and Yagoua in the Arid Sahelian Plain Zone.

Scientific-Article Juillet 2025, Volume 07, Issue 03

## Abstract

Seasonal floods affect ecosystems and local populations in the Sahelian zones in varying ways. This study analyzes the impact of these floods on biodiversity and the resilience of local communities in Koza (mountainous zone) and Yagoua (plain zone). Through a combined approach involving field observations, local surveys, and climate data analysis, it was determined that in Koza, an average loss of seven plant species occurs after flooding events, along with a significant decline in vegetation cover (from 30% to 17.5%). However, some pioneer species (Cenchrus biflorus, Panicum laetum) rapidly recolonize the affected areas. In Yagoua, although vegetation is also affected, the loss in species richness is lower, and the vegetation cover remains relatively high after the rainy season. Moreover, the persistence of water creates favorable conditions for the regeneration of aquatic and semi-aquatic ecosystems (Echinochloa stagnina, Oryza longistaminata). Ecosystem regeneration time is longer in Koza (18 months) compared to Yagoua (12 months). More than 40% of natural habitats are destroyed after floods in Koza, compared to 25% in Yagoua. Seasonal migration is a major adaptive response, with 60% of animal species in Koza and 50% in Yagoua shifting their habitats post-flooding. The presence of pioneer species is more significant in Yagoua (12 species/ha) than in Koza (8 species/ha), promoting faster recolonization of disturbed environments. Seasonal floods have notable effects on terrestrial biodiversity in both regions studied, but the impact is more severe in Koza due to erosion and the low resilience of mountain ecosystems. Yagoua demonstrates a higher regenerative capacity, supported by greater biodiversity and soil conditions more conducive to revegetation.
<figure><img src="image_8.png" /></figure>

Sahel Nature Consulting Revue (ISSN : 1401-0006 March 2025)

Dr. Eng. Dzokom Alexis, M.E.,
M.Rl., Ph.D.,
Chief Editor

Mrs. Yakadam Charlotte B., M.Sc
(Maroua)

Managing Editor & Editorial Board

1. Dr. Ibrahim Koskossi Koras,
   M.Sc, Ph.D., (U.K),
   University of Bahrain,
   Kingdom of Bahrain,

2. Dr. Wassou Belmind, Ph.D.
   (Cambridge),
   University of Malaya,
   Malaysia.

3. Prof. Darman D.R.,
   National Advanced School of
   Engeneering,

University of Maroua (UMa),

4. Prof. Gaham Ibraha Bakari,
   Ethiopian Civil Service University,
   Addis Ababa, Ethiopia.

5. Dr. Kodji Ezechiel,
   Humanitarian services,
   Maroua,
   Cameroon.

Peer Reviewed & Indexed

Sahel Nature Consulting Revue

Indexed By:

<figure><img src="image_9.png" /></figure>

HAL
science ouverte

<figure><img src="image_10.png" /></figure>

Academia.edu

Share Research

Google Scholar

ELSEVIER
SSRN
tomorrow's research today

ResearchGate
# Seasonal Floods, Terrestrial Biodiversity Survival Indices, and Local Population Resilience: Case Study of Koza in the Arid Sahelian Mountain Zone and Yagoua in the Arid Sahelian Plain Zone

Alexis Dzokom<fnref n="1" />, Jules Balna<fnref n="2" />, Etame Sone Diabe<fnref n="2" />, Anguessin Benjamine<fnref n="1" />

Corresponding author: dzokomalexis@gmail.com

## Abstract

Seasonal floods affect ecosystems and local populations in the Sahelian zones in varying ways. This study analyzes the impact of these floods on biodiversity and the resilience of local communities in Koza (mountainous zone) and Yagoua (plain zone). Through a combined approach involving field observations, local surveys, and climate data analysis, it was determined that in Koza, an average loss of seven plant species occurs after flooding events, along with a significant decline in vegetation cover (from 30% to 17.5%). However, some pioneer species (*Cenchrus biflorus*, *Panicum laetum*) rapidly recolonize the affected areas. In Yagoua, although vegetation is also affected, the loss in species richness is lower, and the vegetation cover remains relatively high after the rainy season. Moreover, the persistence of water creates favorable conditions for the regeneration of aquatic and semi-aquatic ecosystems (*Echinochloa stagnina*, *Oryza longistaminata*). Ecosystem regeneration time is longer in Koza (18 months) compared to Yagoua (12 months). More than 40% of natural habitats are destroyed after floods in Koza, compared to 25% in Yagoua. Seasonal migration is a major adaptive response, with 60% of animal species in Koza and 50% in Yagoua shifting their habitats post-flooding. The presence of pioneer species is more significant in Yagoua (12 species/ha) than in Koza (8 species/ha), promoting faster recolonization of disturbed environments. Seasonal floods have notable effects on terrestrial biodiversity in both regions studied, but the impact is more severe in Koza due to erosion and the low resilience of mountain ecosystems. Yagoua demonstrates a higher regenerative capacity, supported by greater biodiversity and soil conditions more conducive to revegetation.

**Keywords:** Seasonal floods, terrestrial biodiversity, resilience, Koza, Yagoua, Sahel, adaptive strategies.

## Introduction

Seasonal floods are a recurrent phenomenon in the Sahelian zones of Cameroon, affecting both biodiversity and local populations. These events are generally triggered by intense rainfall, although their frequency and intensity have been exacerbated by climate

change [10]. Two distinct areas illustrate the complexity of these phenomena: Koza, located in the arid mountainous region of Mayo-Tsanaga, and Yagoua, situated in the arid plain region of Mayo-Danay.

In the Sahelian context, floods are not solely perceived as natural disasters; they are also

<footnote n="1">¹Department of Environmental Sciences, National Advanced School of Engineering, University of Maroua, Cameroon</footnote>

<footnote n="2">²Department of Geography, Faculty of Arts Letters and Social Sciences, University of Maroua, Cameroon</footnote>
## Seasonal Floods, Terrestrial Biodiversity Survival Indices, and Local Population Resilience: Case Study of Koza in the Arid Sahelian Mountain Zone and Yagoua in the Arid Sahelian Plain Zone

© Juillet 2025, Volume 07, Issue 03 | https://sites.google.com/view/sahel-nature-consulting/accueil

seen as events that play a significant role in ecological and social dynamics [14, 13, 15]. Indeed, floods contribute to the renewal of natural resources, soil fertilization, and the regeneration of certain ecosystems [5, 6]. However, these potential benefits often fail to offset the human, economic, and material losses they cause, particularly in contexts where preventive and adaptive capacities remain limited [11].

The terrestrial biodiversity of the Sahelian regions has evolved specific adaptation strategies to cope with extreme conditions, including seasonal flooding. Certain plant and animal species survive through mechanisms such as dormancy, dispersion, or physiological adaptation to hydric variability [8, 9]. Likewise, although vulnerable, local populations adopt various adaptation strategies such as seasonal mobility, food storage, and the diversification of economic activities [1, 2, 3, 7].

The case of Koza illustrates adaptation to a rugged topography, where water runoff is fast and violent, whereas Yagoua highlights

challenges related to the rise of floodwaters from the Logone River and the stagnation of water in the plain. These differences shape the ways in which communities perceive and manage flood events. A comparative analysis of these two cases helps to better understand the dynamic interactions between ecological and social systems in response to floods in the Sahelian environment.

### 1. Materials and Methods

This study on seasonal floods, their impacts on terrestrial biodiversity, and the resilience of local populations in Koza (arid Sahelian mountainous zone) and Yagoua (arid Sahelian plain zone) is based on a methodological approach combining hydrometeorological analyses, ecological inventories, and socio-economic surveys.

#### 1.1. Study Sites

The table below presents the characteristics of seasonal floods in Koza and Yagoua as considered in the study.

<table><caption>Table 1: Characteristics of Seasonal Floods in Koza and Yagoua</caption><thead><tr><td>Parameters</td><td>Koza (Arid Sahelian Mountain Zone)</td><td>Yagoua (Arid Sahelian Plain Zone)</td></tr></thead><tbody><tr><td>Location</td><td>Mandara Mountains (North Cameroon)</td><td>Logone Plain (Far North Cameroon)</td></tr><tr><td>Annual rainfall (mm)</td><td>450 – 700 mm</td><td>600 – 900 mm</td></tr><tr><td>Nature of floods</td><td>Flash floods, intense surface runoff</td><td>Slow-onset floods, Logone River overflow</td></tr><tr><td>Duration of floods</td><td>Short (a few hours to 2 days)</td><td>Long (1 to 4 weeks)</td></tr><tr><td>Flood frequency</td><td>Irregular (due to localized heavy rainfall)</td><td>Annual (linked to Logone River flooding)</td></tr><tr><td>Soil type</td><td>Hard rocky soils, low permeability</td><td>Clay soils with high water retention</td></tr><tr><td>Runoff velocity</td><td>Very rapid (steep slopes)</td><td>Slow (flat terrain, water stagnation)</td></tr><tr><td>Soil erosion</td><td>High (landslides and surface erosion)</td><td>Moderate (flooded soils with limited erosion)</td></tr><tr><td>Impact on agriculture</td><td>Damage to terrace crops</td><td>Loss of recession agriculture crops</td></tr><tr><td>Impact on biodiversity</td><td>Temporary reduction in vegetation</td><td>Proliferation of aquatic and semi-aquatic species</td></tr><tr><td>Health consequences</td><td>Fewer waterborne diseases but injury risks</td><td>High prevalence of malaria and cholera</td></tr></tbody></table>
# Seasonal Floods, Terrestrial Biodiversity Survival Indices, and Local Population Resilience: Case Study of Koza in the Arid Sahelian Mountain Zone and Yagoua in the Arid Sahelian Plain Zone

© Juillet 2025, Volume 07, Issue 03 | https://sites.google.com/view/sahel-nature-consulting/accueil

<table><thead><tr><th></th><th></th><th></th></tr></thead><tbody><tr><td>Local adaptation strategies</td><td>Settlement on elevated ground, terrace farming</td><td>Floating crop systems, livelihood diversification</td></tr><tr><td>Flood prevention infrastructure</td><td>Weak (lack of dikes or retention basins)</td><td>Presence of natural dikes, but insufficient infrastructure</td></tr></tbody></table>

This table highlights the differences in hydrological dynamics of flooding in Koza and Yagoua, with distinct impacts on the environment and local populations.

* **Koza (Far North Cameroon):** A mountainous area where hydrology is characterized by rapid runoff and torrential flows.

* **Yagoua (Logone Plain):** A lowland area where floods result primarily from the overflow of the Logone River and the saturation of clay soils with low infiltration capacity.

<figure><img src="image_11.png" /><figcaption>Figure 1: Study Area</figcaption></figure>

The climatic conditions of these zones are typical of the Sahel, characterized by a short rainy season (June to September) and high interannual variability in precipitation [11].

## 1.2. Data Collection

* **Hydrometeorological data:** Rainfall (mm), water levels (cm), and flood duration (days), obtained from local meteorological stations and reports from the National Meteorology Directorate.

* **Ecological data:** Terrestrial biodiversity survival indices, including vegetation density, species richness, and the presence of flood-adapted indicator species [8, 9].

* **Socio-economic data:** Local population adaptation strategies, analyzed through surveys and semi-structured interviews with households and local farmer organizations [1, 2, 3, 7].

## 1.3. Analytical Methods

### 1.3.1. Analysis of Hydrometeorological Dynamics

Rainfall and hydrological data were collected over a 20-year period (2000–2020) to assess climatic trends and flood frequency. Statistical analysis was conducted using the R software and time-series modeling approaches [14, 12, 15].

### 1.3.2. Assessment of Terrestrial Biodiversity

The impact of floods on biodiversity was assessed using three main criteria:

* **Species richness:** Floristic and faunal surveys were conducted along 500 m² transects in Koza and 1 ha plots in Yagoua, following the method described in [4].

* **Species survival strategies:** Resilient species were identified through field observations and botanical databases [5, 6].
Seasonal Floods, Terrestrial Biodiversity Survival Indices, and Local
Population Resilience: Case Study of Koza in the Arid Sahelian Mountain
Zone and Yagoua in the Arid Sahelian Plain Zone

© Juillet 2025, Volume 07, Issue 03 | | https://sites.google.com/view/sahel-nature-consulting/accueil

* **Post-flood dynamics:** Ecosystem regeneration was monitored over a 12-month period following flood events.

**1.3.3. Assessment of Local Population Resilience**

Socio-economic resilience was evaluated
through:

* Surveys of 200 households (100 in Koza, 100 in Yagoua) focusing on adaptation strategies to floods (mobility, food storage, income diversification).

* Interviews with local authorities and disaster management experts to understand existing local policies for prevention and adaptation [11].

* Loss and damage analysis through the estimation of agricultural losses and damage to infrastructure.

**2. Results and Discussion**

The analysis of seasonal floods in Koza and
Yagoua reveals differentiated impacts on
terrestrial biodiversity and local populations.

<figure><img src="image_12.png" /><figcaption>Photo 1: Seasonal Flooding in (a) Koza and (b) Yagoua</figcaption></figure>

This section presents the main findings and
contextualizes them with reference to
existing literature.

**2.1. Characteristics of Seasonal Flooding**

The plotted curves illustrate climatic trends
and flood frequency in Koza and Yagoua
over the 2000–2020 period.

<figure><img src="image_13.png" /><figcaption>Figure 2: Trends in Precipitation, Water Levels, and Flood Duration in Koza and Yagoua (2000–2020)</figcaption></figure>
Seasonal Floods, Terrestrial Biodiversity Survival Indices, and Local Population Resilience: Case Study of Koza in the Arid Sahelian Mountain Zone and Yagoua in the Arid Sahelian Plain Zone

© Juillet 2025, Volume 07, Issue 03 | https://sites.google.com/view/sahel-nature-consulting/accueil

These trends allow for the evaluation of climatic variability and flood frequency in these two distinct Sahelian zones.

The table below details the characteristics

of seasonal floods in Koza and Yagoua, providing average values for key parameters before and after rainfall events.

<table><caption>Table 2: Characteristics of Seasonal Floods in Koza and Yagoua</caption><thead><tr><td>Parameters</td><td>Koza (Arid Sahelian Mountain Zone)</td><td>Yagoua (Arid Sahelian Plain Zone)</td></tr></thead><tbody><tr><td>Annual rainfall (mm)</td><td>575 ± 125 mm</td><td>750 ± 150 mm</td></tr><tr><td>Average runoff (% of rainfall)</td><td>45 ± 10%</td><td>30 ± 8%</td></tr><tr><td>Average slope gradient (%)</td><td>25 ± 5%</td><td>3 ± 1%</td></tr><tr><td>Soil permeability before rainfall (mm/h)</td><td>6 ± 1 mm/h</td><td>3 ± 0.5 mm/h</td></tr><tr><td>Soil permeability after rainfall (mm/h)</td><td>4 ± 0.8 mm/h</td><td>1.5 ± 0.3 mm/h</td></tr><tr><td>Average erosion rate before rainfall (t/ha/year)</td><td>9 ± 2 t/ha/year</td><td>5 ± 1.5 t/ha/year</td></tr><tr><td>Average erosion rate after rainfall (t/ha/year)</td><td>15 ± 4 t/ha/year</td><td>9 ± 2.5 t/ha/year</td></tr><tr><td>Annual number of landslides before rainfall</td><td>3 ± 1</td><td>1 ± 0.5</td></tr><tr><td>Annual number of landslides after rainfall</td><td>9 ± 3</td><td>3 ± 1</td></tr></tbody></table>

Key Findings:

* **Rainfall is more abundant and variable in Yagoua.**

* **Runoff is more intense in Koza** due to steep slopes.

* **Soil permeability decreases after rainfall, more significantly in Yagoua, where clay soils become saturated.**

* **Erosion increases after rainfall,** especially in Koza, where topography amplifies the phenomenon.

* **Landslides occur more frequently after rainfall,** particularly in Koza due to enhanced erosion and steep terrain.

This table highlights the impact of rainfall on the hydrological and geomorphological dynamics in both regions. Overall, hydrometeorological data reveal interannual variability in flooding, with differing trends between the two study areas:

* **In Koza (mountainous zone),** although annual precipitation is moderate (450–700 mm/year), it

results in intense and rapid runoff due to rugged terrain and low-permeability soils. Flood events are therefore short but violent, leading to severe soil erosion and frequent landslides [14, 13, 12, 15].

* **In Yagoua (plain zone),** floods are primarily associated with overflows of the Logone River and the low infiltration capacity of clay soils. These floods are spatially extensive and persist for several weeks, promoting the saturation of agricultural land and prolonged waterlogging [5, 6].

These findings confirm trends observed by [11], which highlight the differentiated effects of climate on hydrological dynamics across Sahelian regions.

## 2.2. Impacts on Terrestrial Biodiversity

The following table provides an overview of the impacts of seasonal flooding on terrestrial biodiversity in Koza and Yagoua, including key environmental and ecological parameters.
Seasonal Floods, Terrestrial Biodiversity Survival Indices, and Local Population Resilience: Case Study of Koza in the Arid Sahelian Mountain Zone and Yagoua in the Arid Sahelian Plain Zone

© Juillet 2025, Volume 07, Issue 03 | https://sites.google.com/view/sahel-nature-consulting/accueil

<table><caption>Table 3: Impacts of Seasonal Floods on Terrestrial Biodiversity</caption><thead><tr><td>Parameters</td><td>Koza (Arid Sahelian Mountain Zone)</td><td>Yagoua (Arid Sahelian Plain Zone)</td></tr></thead><tbody><tr><td>Plant species richness before rainfall (species/ha)</td><td>25 ± 5 species</td><td>40 ± 8 species</td></tr><tr><td>Plant species richness after rainfall (species/ha)</td><td>18 ± 4 species</td><td>35 ± 7 species</td></tr><tr><td>Vegetation cover before rainfall (%)</td><td>30 ± 6%</td><td>50 ± 8%</td></tr><tr><td>Vegetation cover after rainfall (%)</td><td>17.5 ± 5%</td><td>40 ± 7%</td></tr><tr><td>Soil instability after rainfall (index 0–10)</td><td>8 ± 1.5</td><td>5 ± 1</td></tr><tr><td>Vegetation ecosystem regeneration time (months)</td><td>18 ± 4 months</td><td>12 ± 3 months</td></tr><tr><td>Animal ecosystem dynamics (habitat loss after flooding, %)</td><td>40 ± 8%</td><td>25 ± 5%</td></tr><tr><td>Animal species adaptation (seasonal migration, % of species)</td><td>60 ± 10%</td><td>50 ± 8%</td></tr><tr><td>Presence of pioneer species after floods (species/ha)</td><td>8 ± 2 species</td><td>12 ± 3 species</td></tr></tbody></table>

### 2.2.1. Environmental Factors

Rainfall is higher in Yagoua, with more moderate runoff compared to Koza, where steep slopes promote rapid water discharge. Soil permeability significantly decreases after rainfall, especially in Yagoua, where the clayey texture favors water stagnation. Erosion is more pronounced in Koza, with severe land degradation following rainfall events.

### 2.2.2. Impacts on Plant Biodiversity

In Koza, an average of seven plant species are lost following floods, along with a significant reduction in vegetation cover (from 30% to 17.5%). In Yagoua, although vegetation is also affected, the loss of species richness is lower, and vegetation cover remains relatively high after the rainy season. Ecosystem regeneration takes longer in Koza (18 months compared to 12 months in Yagoua).

### 2.2.3. Impacts on Animal Biodiversity

More than 40% of natural habitats are destroyed after flooding in Koza, compared to 25% in Yagoua. Seasonal migration is a key

adaptation strategy, with 60% of animal species in Koza and 50% in Yagoua relocating after floods. The presence of pioneer species is more pronounced in Yagoua (12 species/ha) than in Koza (8 species/ha), facilitating quicker recolonization of disturbed areas.

Seasonal floods have marked effects on terrestrial biodiversity in both zones studied, but the impact is more severe in Koza due to erosion and the low resilience of mountainous ecosystems. Yagoua displays greater regeneration capacity, supported by richer biodiversity and soils more favorable to revegetation. The biodiversity assessment in both zones revealed several adaptation strategies among terrestrial species in response to flooding.

### 2.2.4. Species Richness and Vegetation Dynamics

In Koza, vegetation cover significantly declines after flooding due to erosion and soil instability. However, certain pioneer species (*Cenchrus biflorus*, *Panicum laetum*) rapidly recolonize affected areas, suggesting ecological resilience mechanisms [8, 9]. In
# Seasonal Floods, Terrestrial Biodiversity Survival Indices, and Local Population Resilience: Case Study of Koza in the Arid Sahelian Mountain Zone and Yagoua in the Arid Sahelian Plain Zone

© Juillet 2025, Volume 07, Issue 03 | | https://sites.google.com/view/sahel-nature-consulting/accueil

Yagoua, persistent water creates favorable conditions for the regeneration of aquatic and semi-aquatic ecosystems, including *Echinochloa stagnina* and *Oryza longistaminata*. Nevertheless, significant losses are observed in food crops (e.g., rice, sorghum) and pasture areas, reducing biodiversity resources vital to local livelihoods [1, 2, 3, 7].

These findings are consistent with those of [5, 6], who note that the impact of flooding on Sahelian vegetation depends largely on soil type and duration of submersion.

<figure><img src="image_14.png" /><figcaption>**Photo 2: Dominant Vegetation Cover Following Seasonal Floods: (a) Oryza longistaminata in Yagoua and (b) Panicum laetum in Koza**</figcaption></figure>

## 2.2.5. Adaptations of Animal Species

Flooding temporarily alters the distribution of terrestrial fauna. In Koza, species such as the Cape hare (*Lepus capensis*) and certain antelopes migrate to higher grounds, while aquatic reptiles and insects thrive in temporarily inundated areas. In Yagoua, the proliferation of mosquitoes (*Anopheles gambiae*) and amphibians (*Hoplobatrachus occipitalis*) following flood events fosters the emergence of new ecological equilibria but also poses health risks for local human populations. These findings align with the work of [8], which demonstrates that Sahelian fauna adopt migratory and behavioral

strategies to adapt to hydrological disturbances.

## 2.3. Resilience of Local Populations

### 2.3.1. Adaptation Strategies of Local Communities

In Koza, 65% of residents diversify their income sources (livestock rearing, small trade, handicrafts) to better cope with flooding, compared to 50% in Yagoua. Terrace farming is more prevalent in Koza (40% of farmers), serving as an effective strategy to reduce soil erosion. Utilizing topographical relief for flood protection is also more common in Koza (50% of residents), whereas only 20% in Yagoua adopt this approach due to the flat terrain.

### 2.3.2. Vulnerabilities of Local Populations

Post-flood food insecurity is high in both zones, reaching 55% in Koza and 45% in Yagoua. Waterborne diseases (diarrhea, cholera, malaria) affect a larger proportion of the population in Yagoua (50%) than in Koza (40%), attributable to water stagnation and mosquito proliferation. Housing destruction following floods is more pronounced in Yagoua (60% of households affected), where earthen constructions are more vulnerable to rising waters, compared to 30% in Koza, where housing is better adapted to mountainous relief. Dependence on humanitarian aid is higher in Yagoua (65% of the population receiving aid) than in Koza (50%), indicating greater structural vulnerability in the plains.

The table below details the resilience of local populations to seasonal flooding in Koza and Yagoua, with averages for each analyzed parameter.

<figure><img src="image_15.png" /></figure>
Seasonal Floods, Terrestrial Biodiversity Survival Indices, and Local Population Resilience: Case Study of Koza in the Arid Sahelian Mountain Zone and Yagoua in the Arid Sahelian Plain Zone

© Juillet 2025, Volume 07, Issue 03 | | https://sites.google.com/view/sahel-nature-consulting/accueil

<table><caption>Table 4: Resilience of Local Populations</caption><thead><tr><td>Parameters</td><td>Koza (Arid Sahelian Mountain Zone)</td><td>Yagoua (Arid Sahelian Plain Zone)</td></tr></thead><tbody><tr><td>Livelihood diversification (%)</td><td>65 ± 10%</td><td>50 ± 8%</td></tr><tr><td>Proportion of population practicing terrace farming (%)</td><td>40 ± 5%</td><td>10 ± 3%</td></tr><tr><td>Proportion of population using relief for flood protection (%)</td><td>50 ± 7%</td><td>20 ± 5%</td></tr><tr><td>Practice of seasonal migration to reduce flood exposure (% pop.)</td><td>35 ± 6%</td><td>25 ± 5%</td></tr><tr><td>Access to drainage infrastructure and water management (% pop.)</td><td>20 ± 4%</td><td>35 ± 7%</td></tr><tr><td>Post-flood food insecurity rate (%)</td><td>55 ± 10%</td><td>45 ± 8%</td></tr><tr><td>Incidence of waterborne diseases post-flood (% population affected)</td><td>40 ± 8%</td><td>50 ± 9%</td></tr><tr><td>Rate of housing destruction post-flood (% population affected)</td><td>30 ± 6%</td><td>60 ± 10%</td></tr><tr><td>Level of dependence on humanitarian aid post-flood (% pop. aided)</td><td>50 ± 9%</td><td>65 ± 10%</td></tr><tr><td>Existence of local prevention and planning policies (scale 0-10)</td><td>3 ± 1.5</td><td>4 ± 1.2</td></tr><tr><td>Level of community awareness of climate risks (% population aware)</td><td>45 ± 8%</td><td>52 ± 7%</td></tr></tbody></table>

### 2.3.3. Limitations of Local Strategies

The level of flood prevention and management remains very low in both zones, scoring 3/10 in Koza and 4/10 in Yagoua, indicating weak local authority involvement in flood management. Community awareness of climate risks is limited (45% in Koza and 52% in Yagoua), which reduces the

effectiveness of implemented adaptation measures.

The curves illustrating the impacts of seasonal flooding on terrestrial biodiversity in Koza and Yagoua according to key environmental and ecological parameters allow for the establishment of a trend analysis:

<figure><img src="image_16.png" /><figcaption>Figure 3: Impacts of Seasonal Flooding on Terrestrial Biodiversity in Koza and Yagoua</figcaption></figure>

The curves depicting the impacts of seasonal flooding on terrestrial biodiversity in Koza and Yagoua show that Yagoua receives more precipitation, whereas Koza experiences higher runoff due to its mountainous terrain.

Soil erosion and landslides are more pronounced in Koza, where the topography exacerbates these phenomena, while Yagoua exhibits richer biodiversity and better vegetation cover. Soil instability and
ecosystem regeneration are more problematic
in Koza, where soil recovery is slower;
however, animal species show stronger
adaptation in Koza, with some having
developed more robust survival mechanisms.

2.3.3.1. Population Adaptation Strategies
to Flooding

Populations in Koza and Yagoua develop different adaptation strategies to seasonal flooding, yet these remain limited in face of the severity of impacts. Koza relies more on terrace farming and exploitation of relief, whereas Yagoua suffers from greater structural vulnerability due to its flat terrain and water stagnation. Local prevention and land management policies remain insufficient, and public health issues following floods are concerning, necessitating improved awareness and more structured governmental actions. Survey analyses reveal that resilience strategies vary according to local constraints:

* In Koza, communities exploit the relief to reduce flood exposure by building shelters on higher grounds. Terrace farming is also a common adaptive technique, helping to limit erosion and stabilize soils.

* In Yagoua, residents develop adaptation strategies based on livelihood diversification (temporary fishing, floating crops). However, heavy dependence on recession agriculture and grazing lands renders populations more vulnerable to prolonged flooding [1, 2, 3, and 7].

These findings confirm observations by [11],
which emphasize that resilience in the Sahel
relies on a combination of agricultural,
economic, and social strategies adapted to
climatic conditions.

2.3.3.2. Vulnerabilities and Limitations of
Local Strategies

Despite observed adaptive capacities, several
constraints limit population resilience:

*   **Food insecurity:** Significant agricultural losses reduce food stocks and increase dependence on external aid.

*   **Health issues:** Water stagnation in Yagoua fosters proliferation of waterborne diseases (cholera, malaria).

*   **Lack of prevention policies:** Communities report deficits in appropriate infrastructure (dikes, early warning systems) and institutional support.

These challenges are also highlighted by [15],
who stress the necessity for strengthened
local governance to improve climate risk
management in the Sahel.

Given projections of increased frequency and
intensity of extreme climatic events [10], it is
essential to reinforce local risk management
policies and invest in adequate infrastructure.
Solutions such as natural dikes, early warning
systems, and economic diversification could
enhance Sahelian populations' resilience to
future floods.

Conclusion and Recommendations

This study highlights the diverse impacts of
seasonal flooding on ecosystems and local
populations in Koza and Yagoua. While some
species and communities develop effective
adaptation strategies, significant
vulnerabilities persist, particularly regarding
food security and public health.

The analysis of seasonal flooding in Koza
(arid mountainous Sahelian zone) and
Yagoua (arid Sahelian plain zone) reveals
contrasting impacts on terrestrial biodiversity
and local population resilience.
Seasonal Floods, Terrestrial Biodiversity Survival Indices, and Local
Population Resilience: Case Study of Koza in the Arid Sahelian Mountain
Zone and Yagoua in the Arid Sahelian Plain Zone

© Juillet 2025, Volume 07, Issue 03 | | https://sites.google.com/view/sahel-nature-consulting/accueil

At Koza, floods are brief but intense, causing severe erosion and landslides. In Yagoua, floods are more prolonged and primarily result from Logone River overflows, promoting soil waterlogging and stagnation.

Koza's ecosystems suffer marked degradation post-flood, but some pioneer species ensure rapid regeneration. Yagoua's biodiversity adapts better through the persistence of semi-aquatic species, although staple crops and grazing lands experience significant losses.

Adaptation strategies differ by local conditions: elevated construction and terrace farming in Koza; livelihood diversification and floating agriculture in Yagoua. Nevertheless, vulnerability remains high due to agricultural losses, health problems linked to stagnant waters, and insufficient infrastructure. The study thus confirms that Sahelian floods, although recurrent, do not uniformly affect ecosystems and human communities. Resilience depends strongly on environmental conditions and local adaptation strategies.

Recommendations

To address the identified challenges, several
measures can be implemented to strengthen
the resilience of ecosystems and local
populations:

* Establish early warning systems to anticipate floods and minimize human and material losses.

* Construct dikes and retention basins to limit erosion in Koza and better manage stagnant waters in Yagoua.

* Protect and restore natural buffer ecosystems, such as riparian forests and wetlands, which play key roles in flood absorption.

* Promote adapted agriculture, such as agroforestry and moisture-tolerant crops in the plains.

* Train communities in sustainable agricultural and pastoral practices under climatic variability.

* Raise awareness about health risks related to flooding (safe drinking water, control of waterborne diseases).

* Encourage economic diversification to reduce dependence on flood-vulnerable crops.

* Integrate climate risk considerations into land-use planning, especially by avoiding urbanization in flood-prone areas.

* Foster partnerships between scientific institutions and local communities to co-develop effective adaptation strategies.

These recommendations aim to improve seasonal flood management while ensuring biodiversity conservation and the well-being of local populations. An integrated approach combining technical solutions and indigenous knowledge appears key to successful adaptation to climate change challenges in the Sahel.

Acknowledgments

The author wishes to express deep gratitude to all individuals and institutions who contributed, directly or indirectly, to the completion of this article. My sincere thanks go to the local communities of the Cameroonian Sahel for their invaluable collaboration and the sharing of indigenous knowledge, which greatly enriched this study.

I also extend my appreciation to
environmental experts, agents of
decentralized state technical services, and
leaders of farmers' organizations for their
insightful contributions during field surveys.

Special thanks are due to the academic and
research institutions that supported this
endeavor, notably through the provision of
Seasonal Floods, Terrestrial Biodiversity Survival Indices, and Local
Population Resilience: Case Study of Koxa in the Arid Sahelian Mountain
Zone and Yagoua in the Arid Sahelian Plain Zone

© Juillet 2025, Volume 07, Issue 03 | | https://sites.google.com/view/sahel-nature-consulting/accueil

data, infrastructure, and high-quality scientific
supervision.

Finally, I express my gratitude to the technical and financial partners without whom this research would not have been possible. Their support has been instrumental in strengthening local capacities for sustainable environmental management and socio-ecological resilience.

Reference

[1]. Alexis Dzokom, Roger Djouldé Darman (2025). *Seasonal Droughts and Aquifer Biodiversity Survival Indices: Case of the Sahelian Wetland of Lake Chad-Logone-Waza*. North American Journal of Welsh Studies, In press, 05 (02), 1-11.

[2] Batterbury, S. (2001). *Landscapes of diversity: a local political ecology of livelihood diversification in south-western Niger*. Ecumene, 8(4), 437-464.

[3] Batterbury, S., & Warren, A. (2001). *The African Sahel 25 years after the great drought: assessing progress, moving forward*. Global Environmental Change, 11(1), 1-8.

[4] Braun-Blanquet, J. (1932). *Plant Sociology: The Study of Plant Communities*. McGraw-Hill Book Company.

[5] Descroix, L., & Genthon, P. (2011). *La variabilité climatique au Sahel : tendances, cycles et incertitudes*. Sécheresse, 22(1), 51-60.

[6] Descroix, L., Genthon, P., Amogu, O., Rajot, J., & Sighomnou, D. (2011, December). *The highest red flood of the Niger River ever recorded at Niamey: climate change or land use change?* In AGU Fall Meeting Abstracts (Vol. 2011, pp. H43I-1347).

[7] Dzokom, A., Djoulde, D. R., Jules, B., & Watang, Z. F. (2024, October). *Caracteristiques, Perceptions Des Changements Climatiques En Zone Sahelienne Camerounaise Et Strategies D'adaptation Des Organisations Paysannes in Changement Climatique*, Ressources Naturelles, Agriculture, Sante Et Developpement Durable.

GEOPORO. Volume: 2 (Vol. 3, N°
01.) Pp. 192-203.

[8] Hiernaux, P., & Turner, M. D. (1996). *The Effect of Clipping on Growth and Nutrient Uptake of Sahelian Annual Rangelands*. Journal of Applied Ecology, 33(2), 387–399.
https://doi.org/10.2307/2404760

[9] Hiernaux, P., & Turner, M. (2002). *The effect of clipping on growth and nutrient uptake of Sahelian annual rangelands*. Journal of Ecology, 90(6), 970-982.

[10] IPCC (Intergovernmental Panel on Climate Change). (2019). *Special Report on Climate Change and Land*. IPCC, Geneva.

[11] Lebel, T., & Ali, A. (2009). *Recent trends in the Central and Western Sahel rainfall regime* (1990–2007). Journal of Hydrology, 375(1-2), 52-64.

[12] Lienou, G., Mahé, G., Paturel, J. E., Servat, E., Sighomnou, D., Ekodeck, G. E., ... & Dieulin, C. (2008). *Evolution des régimes hydrologiques en région équatoriale camerounaise: un impact de la variabilité climatique en Afrique équatoriale? Hydrological Sciences Journal*, 53(4), 789-801.

[13] Mahé, G., Diello, P., Paturel, J. E., Barbier, B., Karambiri, H., Dezetter, A., ... & Rouché, N. (2010). *Baisse des pluies et augmentation des écoulements au Sahel: impact climatique et anthropique sur les écoulements du Nakambe au Burkina Faso*. Sécheresse, 21(4), 330-332.

[14] Mahé, G., Lienou, G., Descroix, L., Bamba, F., Paturel, J. E., Laraque, A., ... & Khomsi, K. (2013). *Impact du changement climatique sur le régime hydrologique du Sahel*. Hydrological Sciences Journal, 58(4), 746-765.

[15] Mahé, G., Lienou, G., Descroix, L., Bamba, F., Paturel, J. E., Laraque, A., ... &
Seasonal Floods, Terrestrial Biodiversity Survival Indices, and Local
Population Resilience: Case Study of Koxa in the Arid Sahelian Mountain
Zone and Yagoua in the Arid Sahelian Plain Zone

© Juillet 2025, Volume 07, Issue 03 | | https://sites.google.com/view/sahel-nature-consulting/accueil

Khomsi, K. (2013). *The rivers of Africa: witness of climate change and human impact on the environment.* Hydrological Processes, 27(15), 2105-2114.