Study of Digital Surface Data for Soils and Flood Risk Areas Mapping in Sudano-Sahelian Zone (Mayo-Danay Division, Far North Cameroon)

In general, living close to a river is advantage, but there is always of flooding risk, that recurrence in recent decades provokes serious material damage and loss of life. Thus, in order to protect environmental health, economic viability and human activity zones of Mayo-Danay, a careful study of components of natural environment, mainly soil, has proved essential. Clearly, use of GIS in management of natural disasters is most relevant method, designed on integration, Multicriteria Analysis (MCA) and spatial data. Thus, Digital Elevation Model is obtained by manual digitization of contour lines, in order to define the large pedological sets on which wells have been opened, profiles described, soil samples taken and analyzed in laboratory. Main results reveal that soils are sandy to clayey, with neutral and basic pH (7 to 8), high CEC and low organic matter. While, quartz is predominant, associated with smectites, illites, feldspars and iron oxyhydroxides. Updated soil map shows five soil units (1) vertisols with hydromorphic characters (26%), (2) tropical ferruginous soils (32%), (3) less evolved hydromorphic soils (15%), (4) halomorphic vertic soils (9%), and (5) hydromorphic vertic soils (18%). It is an excellent tool for work and research, that responds to agronomic and development problems. It is therefore an excellent tool for work and research, which responds to agronomic and development problems. The multi-criteria spatial analysis establishes hazard and vulnerability, crossing of which gives of flood risk areas map, according to hazard level, very high (12%), high (16%), moderate (14%), low (30%) and very low (28%) risks. For this purpose, it emerges that rainfall is relatively low (700 mm/year), but falls very abruptly during short periods, at high intensity with flows exceeding the infiltration capacities. Morphology of low-slope "yayrés" (280 m) (2‰) is bordered by high landscape (500 to 1400 m) that prevent flow of many rivers that converge into plain. Sandy soils dominated by quartz favor fast rising in water table, while very clayey soils governed by 2/1 clayey (smectites) whose behavior induce waterproofing and intense surface runoff that generate flooding. Evidently, land use change leads to transformation of natural spaces into agricultural and urban environments, which makes soils more compact and impermeable, favorable to flooding. Keywords Soil; Flood risks; Mapping; Mayo-Danay Division; Spatial data DOI: https://doi.org/10.23953/cloud.ijarsg.501

PENGARUH PENGERINGAN CONTOH TANAH TERHADAP BEBERAPA SIFAT FISIK DAN KIMJA TANAH BERSIFAT VERTIK SERTA KLASlFIKASINYA MENURUT TAKSONOMI TANAH

This laboratory experiment was carried out to study the effect of soil samples drying on the physical and chemical properties of vertic soils and their classification according to soil taxonomy. Usually, soil analysis is held on samples in air-dried condition. Clays of some soil types, however, have irreversible properties upon drying which can cause a bias in the measurement results and classification outputs of the soils. To study the irreversibility of clays upon drying, 25 samples of vertic soils were treated in moist and air-dried conditions prior to analysis. The statistical procedure of Match Pair Comparison was used to test the effect of the treatments. The results showed that the irreversibility of day upon drying was reflected in the measured soil properties except for exchangeable-A! and -K, organic-C. and soil-CEC. Nevertheless, the intensity of the day irreversibility of the vertic soils studied was low. Therefore, the drying treatment did not affect their classification outputs.