@article{fdi:010079695,
  title = {{M}echanisms of lateral and linear extension of gullies (dongas) in a subhumid grassland of {S}outh {A}frica},
  author = {{P}odwojewski, {P}ascal and {J}aneau, {J}ean-{L}ouis and {C}aquineau, {S}andrine and {H}ughes, {J}.},
  editor = {},
  language = {{ENG}},
  abstract = {{T}he formation of deep gullies (called 'dongas' locally) in rangeland in {K}wa{Z}ulu-{N}atal {P}rovince in {S}outh {A}frica is a natural phenomenon. {T}hese {U}-shaped, very wide gullies have considerable lateral expansion due to the episodic collapse of sidewalls. {T}he dongas have developed in duplex soils such as {L}uvisols and {L}ixisols formed on {P}ermian sedimentary rocks or unconsolidated {Q}uaternary colluvium. {T}his study combined morphological, mineralogical and chemical characterization with measurements of grain-size content, structural stability and the complete shrinkage curve to detect changes in soil properties of the different horizons located in the gully banks. {T}he different soil horizons present clear and sharp differences in physical and mineralogical properties. {T}he topsoil with complete grass cover is very resistant to soil detachment. {H}owever, the leached {E} horizon and the {BC} horizon have low structural stability. {T}he soil profile down to and including the {B}t horizon contains exclusively illite in the clay fraction, while the {BC} colluvial layer and the {C} horizon (mudstone) contain expandable interstratified illite-smectite. {T}he {B}t horizon has a high water content at saturation and high shrinkage, while the {BC} and {C} horizons have a high residual shrinkage and a very low water content at saturation. {B}ecause this type of gully expansion is not significantly linked to slope value or the stream power index ({SPI}) at the gully head, to land-use change, high rainfall intensities or the threshold of concentrated runoff being exceeded at the gully head, other causes were investigated. {I}t was concluded that the heterogeneity between horizons with different mineralogical properties and structural stabilities, soil types and parent material, anisotropic water-saturation and shrink-swell properties are of major importance. {T}his heterogeneity between different soil horizon morphologies and their physical properties can explain why the relationship between the critical slope and the drainage area for gully initiation showed a threshold for gullying much lower than that found elsewhere.},
  keywords = {soil properties ; gully extension ; shrink-swell ; rangeland ; {S}outh {A}frica ; {AFRIQUE} {DU} {SUD} ; {KWAZULU} {NATAL} {PROVINCE}},
  booktitle = {},
  journal = {{E}arth {S}urface {P}rocesses and {L}andforms},
  volume = {45},
  numero = {13},
  pages = {3202--3215},
  ISSN = {0197-9337},
  year = {2020},
  DOI = {10.1002/esp.4960},
  URL = {https://www.documentation.ird.fr/hor/fdi:010079695},
}