Neotectonics and pastoralism: How they impact flood regimes in Madagascar's highlands

Miétton, Michel; Gunnell, Yanni; Andriamitia, Jocelyn; Crouzet, Christian; Montade, Vincent; Jouannic, Gwénolé; Nicoud, Gérard; Razafimahefa, Reine

doi:10.1016/j.scitotenv.2020.140633

Cited by 3 publications

(8 citation statements)

References 54 publications

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“…Similar measurements for the Bevava and Sahamaloto reservoirs in the lake Alaotra region indicate current erosion rates of around 1 000 mm kyr −1 (Mietton et al., 2020, 2006). These higher rates in the lake Alaotra region were linked to high lavaka densities (Mietton et al., 2020, 2006). Brosens et al.…”

Section: Discussionmentioning

confidence: 63%

“…While reliable regional estimates of current erosion and sediment export rates are not available for most regions in Madagascar, there are indications that current sediment export rates rates exceed long‐term erosion rates by 1 or 2 orders of magnitude in some places. For the Ikopa catchment in the central highlands near Antananarivo, a current erosion rate of 200 mm kyr −1 was derived from suspended sediment loads (360 t km −2 year −1 assuming a bulk density (

ρ

Section: Discussionmentioning

confidence: 99%

“…For the Ikopa catchment in the central highlands near Antananarivo, a current erosion rate of 200 mm kyr −1 was derived from suspended sediment loads (360 t km −2 year −1 assuming a bulk density (

ρ

) of 1.8 t m −3 , Mietton et al., 2020). Similar measurements for the Bevava and Sahamaloto reservoirs in the lake Alaotra region indicate current erosion rates of around 1 000 mm kyr −1 (Mietton et al., 2020, 2006). These higher rates in the lake Alaotra region were linked to high lavaka densities (Mietton et al., 2020, 2006).…”

Section: Discussionmentioning

confidence: 99%

“…These higher rates in the lake Alaotra region were linked to high lavaka densities (Mietton et al, 2020(Mietton et al, , 2006. catchments.…”

Section: Impact Of Gully Processes On Long-term 10 Be and Current Ero...mentioning

confidence: 99%

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The slow downwearing of Madagascar: Inferring patterns and controls on long‐term basin‐averaged erosion rates from in situ¹⁰Be at the catchment and regional level

Brosens

Cox

Campforts

et al. 2023

Earth Surf Processes Landf

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Cosmogenic nuclide analysis of river sediment provides insight into catchment‐wide erosion rates and dynamics. Here, we investigate spatial patterns and controls on 10Be‐inferred erosion rates in Madagascar, a moderately seismically active microcontinent surrounded by passive margins with locally steep topography and a climate that varies from humid tropical to semiarid. We use a compiled dataset of 99 detrital 10Be measurements, 63 of which are new, covering more than 30% of the country and a wide range of topographic, bioclimatic and geologic characteristics. Overall, 10Be erosion rates are low (2.4–51.1 mm kyr−1), with clear differences between regions. The lowest rates are measured on the central highlands ( ∼ 8 mm kyr−1), in the Alaotra–Ankay graben ( ∼ 11 mm kyr−1) and in the large north‐central catchments ( ∼ 11 mm kyr−1). Higher rates are found on the steep eastern escarpment ( ∼ 20 mm kyr−1), in the northwest ( ∼ 31 mm kyr−1) and in the southwest ( ∼ 29 mm kyr−1). A stepwise linear regression model identified elevation as the main factor associated with variations in 10Be erosion rates (lower rates for higher catchments). Random within‐between statistical models (REWB), on the other hand, indicated that the differences between different regions can be explained by differences in river concavity, seismic events and gully (lavaka) densities, whereas additional variation within regions is only linked to seismicity. We find no correlation between catchment or river steepness and 10Be‐inferred erosion rates. Our results indicate that in Madagascar, long‐term erosion rates are overall low and that simple topography‐based models do not explain variations in rates of landscape change inferred from 10Be concentrations in river sediment. We demonstrate that identifying different regions aids in interpreting spatial patterns of erosion rates and that REWB models can be a powerful tool in deciphering environmental controls on 10Be erosion rates.

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Section: Discussionmentioning

confidence: 63%

ρ

Section: Discussionmentioning

confidence: 99%

ρ

Section: Discussionmentioning

confidence: 99%

“…These higher rates in the lake Alaotra region were linked to high lavaka densities (Mietton et al, 2020(Mietton et al, , 2006. catchments.…”

Section: Impact Of Gully Processes On Long-term 10 Be and Current Ero...mentioning

confidence: 99%

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The slow downwearing of Madagascar: Inferring patterns and controls on long‐term basin‐averaged erosion rates from in situ¹⁰Be at the catchment and regional level

Brosens

Cox

Campforts

et al. 2023

Earth Surf Processes Landf

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“…Sediment core data show that the valley floor has dropped by 15 m in the past 30,000 years ( 95 ). The average subsidence rate is about 0.5 cm per decade, but vertical ground movement rates in some areas are up to twice the long-term average, and hydraulic engineering infrastructure in the area is disrupted by small-scale motions that offset canals and sluices ( 165 ).…”

Section: Resultsmentioning

confidence: 99%

Gullying and landscape evolution: Lavaka in Lac Alaotra, Madagascar shed light on rates of change and non-anthropogenic controls

Cox,

Phillips,

Rakotondrazafy

2024

Sci. Adv.

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Gully evolution remains poorly understood, largely because multidecadal analysis is lacking. Large gullies (called lavaka) that pepper Madagascar’s highlands are generally attributed to human impact; but longitudinal data are few, and anthropogenic causation is inferred not verified. We focus on Lac Alaotra, Madagascar’s largest lake and wetland, its major rice-growing region, and an ecological hotspot surrounded by fault-controlled steep hills with abundant lavaka. Analysis of historical aerial photographs and recent orthoimagery reveals that the proportion of highly active lavaka has decreased since mid-20th century. At the same time, human population, farming intensity, and livestock density have increased exponentially. This suggests that background factors, including seismicity, are primary drivers of lavaka formation. Although human activities may contribute to erosion overall, land management policies that overemphasize human causation of gullying and neglect background forcing factors (in Madagascar and elsewhere) are unlikely to be effective in erosion mitigation.

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A Systematic Review of Water Resources Assessment at a Large River Basin Scale: Case of the Major River Basins in Madagascar

et al. 2022

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Assessing water resources at a large river basin scale is important for having an idea of the water situation and efficient water resources management. What is the most appropriate approach to assess the water resources at a large river basin scale? This paper aims to develop a systematic review on water resources assessment at a large river basin scale, intending to present a new assessment method for the major river basins in Madagascar. This review investigates 40 articles from Google Scholar, Web of Science, and PubMed databases, from 2000 to 2022. This review has demonstrated the necessity of water resources assessment at a large river basin scale in Madagascar. An improvement in the use of multiple GCMs and SWAT models for water resources assessment within the basin was found necessary for appropriate water allocating regimes among upper and lower reaches. Water allocation and water scarcity at the basin level could be addressed by using the inter- and intra-basin approaches. The review concludes that a combination of the SWAT, multiple GCMs, and inter- and intra-basin approaches could be efficiently applied for assessing the water resources at a large basin scale. This review may be of benefit to scientists and water specialists.

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Neotectonics and pastoralism: How they impact flood regimes in Madagascar's highlands

Cited by 3 publications

References 54 publications

The slow downwearing of Madagascar: Inferring patterns and controls on long‐term basin‐averaged erosion rates from in situ¹⁰Be at the catchment and regional level

The slow downwearing of Madagascar: Inferring patterns and controls on long‐term basin‐averaged erosion rates from in situ¹⁰Be at the catchment and regional level

Gullying and landscape evolution: Lavaka in Lac Alaotra, Madagascar shed light on rates of change and non-anthropogenic controls

A Systematic Review of Water Resources Assessment at a Large River Basin Scale: Case of the Major River Basins in Madagascar

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Neotectonics and pastoralism: How they impact flood regimes in Madagascar's highlands

Cited by 3 publications

References 54 publications

The slow downwearing of Madagascar: Inferring patterns and controls on long‐term basin‐averaged erosion rates from in situ10Be at the catchment and regional level

The slow downwearing of Madagascar: Inferring patterns and controls on long‐term basin‐averaged erosion rates from in situ10Be at the catchment and regional level

Gullying and landscape evolution: Lavaka in Lac Alaotra, Madagascar shed light on rates of change and non-anthropogenic controls

A Systematic Review of Water Resources Assessment at a Large River Basin Scale: Case of the Major River Basins in Madagascar

Contact Info

Product

Resources

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The slow downwearing of Madagascar: Inferring patterns and controls on long‐term basin‐averaged erosion rates from in situ¹⁰Be at the catchment and regional level

The slow downwearing of Madagascar: Inferring patterns and controls on long‐term basin‐averaged erosion rates from in situ¹⁰Be at the catchment and regional level