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Abstract
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Article Information:
Gully Growth Patterns and Soil Loss under Rainfall at Urban Underground Drainage Construction Site, Uyo
O.E. Essien and I.A. Essen
Corresponding Author: O.E. Essien
Submitted: November 09, 2011
Accepted: December 09, 2011
Published: August 15, 2012 |
Abstract:
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This study investigated, evaluated and modeled patterns of growth of gully morphometric dimension
and soil loss volume under prevailing rainfall on the slopes of land graded for the construction of underground
drainage at Uyo but delayed in completion. Land grading at underground (tunnel) drainage construction site
rendered the exposed surface very impervious but young ephemeral gullies developed due to delays in
completion. Data on gully morphometric dimension, soil loss and depth of rainfall were analyzed using SPSS
ver. 17 statistical package. Mean gully growth in length, width and depth were different at 2.54±0.86,
0.923±0.29 and 0.41±0.11 m, respectively, yielding 3.87±0.08 m2 as mean volume of soil loss at full stage.
Cubic polynomial was best-fit model for growth in length (R2 = 79%) and width (R2 = 69%) using weekly
rainfall for an annual season. All gully sites had constant depth change, better predicted by quadratic (R2 =
13%) than linear (R2 = 9%) functions. Mean volume of soil loss per unit rainfall amount varied with low,
medium and high rainfall amount and was highest at slope bottom (33 cm3/cm) and least at the crest (6.99 cm3/cm) with R2 = 38-34%. Land grading to impervious sublayer produced constant depth change in all gullies
at the sites. The models for morphometric incremental growth and soil loss volume under the rainfall effect was
significantly improved (p<0.05) by bifurcating the lumped annual curve into two growth periods in a year: the
periods for increasing rainfall (from week 10-30) and for receding rainfall (from week 31-43) in a year and
applying quadratic regressing functions on each (R2 = 91-99%). Rainfall was the principal gully factor and
construction delays should be avoided.
Key words: Geometric increment, growth pattern, gully, Land grading, rainfall, soil loss volume, underground drainage
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Cite this Reference:
O.E. Essien and I.A. Essen, . Gully Growth Patterns and Soil Loss under Rainfall at Urban Underground Drainage Construction Site, Uyo. Research Journal of Applied Sciences, Engineering and Technology, (16): 2616-2625.
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ISSN (Online): 2040-7467
ISSN (Print): 2040-7459 |
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