scholarly journals A multi-method approach to analyze changes in gully characteristics between 2009 and 2018 in southeast Nigeria

2021 ◽  
Author(s):  
Ikenna Osumgborogwu ◽  
John Wainwright ◽  
Laura Turbull ◽  
Luke Uzoigwe
Keyword(s):  
Land Use ◽  
Civil War ◽  
Focus Group ◽  
Surface Runoff ◽  
Land Use Changes ◽  
Soil Conditions ◽  
Geotechnical Investigations ◽  
Nigerian Civil War ◽  
Multi Method Approach ◽  
Method Approach

Gully erosion is the dominant environmental problem in southeast Nigeria and has led to loss of human and material resources. In this study, we evaluated changes in gully characteristics in southeast Nigeria between 2009 and 2018 using a multi-method approach including geotechnical investigations, analysis of high-resolution satellite imagery (2 – 5 m) and focus group discussions. Gully numbers increased from 26 to 39 and mean gully length increased from 0.39 to 0.43 km. We found that the soils in the study area have low cohesion and high sand content which make them susceptible to dispersal by erosive forces. Land adjacent to rivers had the highest concentration of gullies, and there was a sharp rise in slope from 10 – 58.2% within a distance less than 500 m from the river. Regarding potential gully-drivers, land-use changes were observed. Non-vegetated lands increased from 58.6 km2 to 144.7 km2 between 2009 and 2018, while reductions in fallowed lands from 281.2 km2 to 57.8 km2 were observed. Results from focus group meetings indicate there was no gullying in the area before the Nigerian civil war. Although war-time activities which led to initiation of oldest gullies have ceased, land-use changes likely increase volume of surface runoff. We infer that interactions between soil conditions which potentially enhance seepage erosion and higher surface runoff resulting from land-use changes have propagated gullying in the study area post-civil war.

The gullies of southeast Nigeria: an ecogeomorphic investigation

2020 ◽  
Author(s):  
Ikenna Osumgborogwu ◽  
John Wainwright ◽  
Laura Turnbull-Lloyd
Keyword(s):  
Land Use ◽  
Civil War ◽  
Focus Group ◽  
Human Activities ◽  
Vegetation Cover ◽  
Land Use Changes ◽  
Slope Angle ◽  
Gully Erosion ◽  
Remotely Sensed Data ◽  
Group Meetings

<p>Gully erosion was unknown in the Orlu area of Southeast Nigeria before the Nigerian civil war (from 1967 to 1970) but has now become endemic and continues to present day.  Human activities are central to this acceleration of erosion due to their intervention with ecogeomorphic processes. This paper aims to improve understanding of ecogeomorphic drivers of gully erosion using case studies from the Orlu area of southeast Nigeria, and to achieve this aim, focus-group meetings and analyses of remotely sensed data were adopted. High-resolution (0.61 – 5 m) satellite imagery for 2009 and 2018 were acquired from different platforms and used for gully mapping and monitoring while ASTAR DEM was used to estimate topological parameters. Upslope contributing areas were produced for two gullies; A and U, while gully evolutions between 2009 and 2018 were related to changes in contributing areas during same time span. Ecogeomorphic and climatic drivers such as vegetation-cover change, slope angle, elevation, rainfall, and nearness to roads and rivers were studied and their associations with gullying established. Vegetation cover was classified into three: non-vegetated, open vegetation and trees while daily surface runoff between 2009 and 2018 was estimated for these vegetation classes using the Curve Number approach. Results from focus-group meetings show that both gullies started in 1969 during the civil war as a result of increase in population density arising from the influx of refugees as well as other military activities. Gully growth was sustained after the civil war was a result of land use changes. Average gully headcut retreat rate between 2009 and 2018 was 64 m yr<sup>-1</sup> and 12.2 m yr<sup>-1</sup> for gully A and U respectively, while a positive correlation was recorded between change in vegetation cover in contributing areas and increase in gullied area with Pearson’s correlation of 0.6 and r<sup>2</sup> of 0.4. The runoff model predicted runoff for only the non-vegetated areas with runoff coefficients ranging from 11.5 % to 22 %. Slope angle, profile and plan curvature had positive associations with gullies while elevation, nearness to rivers and nearness to roads recorded negative correlations with gullies. In conclusion, while geomorphic drivers such as slope angle are preparatory factors, human activities including civil wars and land-use changes are forcing factors of gully erosion. This study has implications for gully remediation especially as regards land use management of upslope contributing areas.</p><p><strong>Keywords: Gully erosion, Ecogeomorphology, upslope contributing area, south east Nigeria</strong></p>

scholarly journals Modelling monthly runoff generation processes following land use changes: groundwater–surface runoff interactions

2004 ◽  
Vol 8 (5) ◽  
pp. 903-922 ◽  
Author(s):  
M. Bari ◽  
K. R. J. Smettem
Keyword(s):  
Land Use ◽  
Water Balance ◽  
Surface Runoff ◽  
Land Use Changes ◽  
Annual Rainfall ◽  
Rainfall Runoff ◽  
Runoff Generation ◽  
Mean Annual Rainfall ◽  
Monthly Runoff ◽  
Stream Bed

Abstract. A conceptual water balance model is presented to represent changes in monthly water balance following land use changes. Monthly rainfall–runoff, groundwater and soil moisture data from four experimental catchments in Western Australia have been analysed. Two of these catchments, "Ernies" (control, fully forested) and "Lemon" (54% cleared) are in a zone of mean annual rainfall of 725 mm, while "Salmon" (control, fully forested) and "Wights" (100% cleared) are in a zone with mean annual rainfall of 1125 mm. At the Salmon forested control catchment, streamflow comprises surface runoff, base flow and interflow components. In the Wights catchment, cleared of native forest for pasture development, all three components increased, groundwater levels rose significantly and stream zone saturated area increased from 1% to 15% of the catchment area. It took seven years after clearing for the rainfall–runoff generation process to stabilise in 1984. At the Ernies forested control catchment, the permanent groundwater system is 20 m below the stream bed and so does not contribute to streamflow. Following partial clearing of forest in the Lemon catchment, groundwater rose steadily and reached the stream bed by 1987. The streamflow increased in two phases: (i) immediately after clearing due to reduced evapotranspiration, and (ii) through an increase in the groundwater-induced stream zone saturated area after 1987. After analysing all the data available, a conceptual monthly model was created, comprising four inter-connecting stores: (i) an upper zone unsaturated store, (ii) a transient stream zone store, (ii) a lower zone unsaturated store and (iv) a saturated groundwater store. Data such as rooting depth, Leaf Area Index, soil porosity, profile thickness, depth to groundwater, stream length and surface slope were incorporated into the model as a priori defined attributes. The catchment average values for different stores were determined through matching observed and predicted monthly hydrographs. The observed and predicted monthly runoff for all catchments matched well with coefficients of determination (R2) ranging from 0.68 to 0.87. Predictions were relatively poor for: (i) the Ernies catchment (lowest rainfall, forested), and (ii) months with very high flows. Overall, the predicted mean annual streamflow was within ±8% of the observed values. Keywords: monthly streamflow, land use change, conceptual model, data-based approach, groundwater

scholarly journals The effect of land uses to change on infiltration capacity and surface runoff at latung sub watershed, Padang City Indonesia

2021 ◽  
Vol 331 ◽  
pp. 08002
Author(s):  
Rusli HAR ◽  
Aprisal ◽  
Werry Darta Taifur ◽  
Teguh Haria Aditia Putra
Keyword(s):  
Land Use ◽  
Surface Runoff ◽  
Land Use Changes ◽  
Curve Number ◽  
Soil Infiltration ◽  
Infiltration Capacity ◽  
Rainwater Infiltration ◽  
Double Ring ◽  
Hydrology Modeling ◽  
Runoff Discharge

Changes in land use in the Air Dingin watershed (DAS) area in Padang City, Indonesia, lead to a decrease in rainwater infiltration volume to the ground. Some land use in the Latung sub-watershed decrease in infiltration capacity with an increase in surface runoff. This research aims to determine the effect of land-use changes on infiltration capacity and surface runoff. Purposive sampling method was used in this research. The infiltration capacity was measured directly in the field using a double-ring infiltrometer, and the data was processed using the Horton model. The obtained capacity was quantitatively classified using infiltration zoning. Meanwhile, the Hydrologic Engineering Center - Hydrology Modeling System with the Synthetic Unit Hydrograph- Soil Conservation Service -Curve Number method was used to analyze the runoff discharge. The results showed that from the 13 measurement points carried out, the infiltration capacity ranges from 0.082 - 0.70 cm/minute or an average of 0.398 cm/minute, while the rainwater volume is approximately 150,000 m3/hour/km2. Therefore, the soil infiltration capacity in the Latung sub-watershed is in zone VI-B or very low. This condition had an impact on changes in runoff discharge in this area, from 87.84 m3/second in 2010 to 112.8 m3/second in 2020 or a nail of 22.13%. Based on the results, it is concluded that changes in the land led to low soil infiltration capacity, thereby leading to an increase in surface runoff.

Sharing a methodology to develop a satisfaction questionnaire in mental health care

2018 ◽  
Vol 68 (suppl 1) ◽  
pp. bjgp18X697421
Author(s):  
Eva Ma ◽  
Rachael Johnson ◽  
Teresa Hagan ◽  
Alex Young ◽  
Rajinder Dhanjal ◽  
...  
Keyword(s):  
Focus Group ◽  
Phase 1 ◽  
Quality Criteria ◽  
Service Users ◽  
Satisfaction Questionnaire ◽  
Care Services ◽  
Health And Social Care ◽  
Multi Method Approach ◽  
High Quality Service ◽  
Method Approach

BackgroundThis paper outlines a multi-method’ process for developing a satisfaction questionnaire (SQ) for completion by service users. Satisfaction is a mark of service quality. Both health and social care services are required to evidence this. Working collaboratively with those who use our services is essential for achieving transformation in healthcare.AimIn developing a SQ, the aim was to collaboratively identify key quality criteria of most importance to service users and carers.MethodIn the absence of a gold standard methodology for developing a SQ, we developed an iterative multimethod’ phased process. Phase 1 involved a focus group, attended by service users and carers (n = 20). Participants at the focus group developed a preliminary list of quality criteria. Phase 2 involved a review of existing feedback questionnaires to supplement our quality criteria, including the Friends & Family Test. Phase 3 aimed to build consensus to refine the criteria, using a process informed by the Delphi technique with participants from a service user forum. The final phase of refinement is now underway.ResultsPreliminary findings highlight the key quality indicators of a high-quality service, as defined by service users and carers.ConclusionIt is useful to adopt and develop an iterative multi-method’ approach involving co-production and consensus building in developing a valid and meaningful SQ.

scholarly journals Increase in surface runoff in the central mountains of Mexico: lessons from the past and predictive scenario for the next century

2010 ◽  
Vol 14 (2) ◽  
pp. 291-300 ◽  
Author(s):  
N. Gratiot ◽  
C. Duvert ◽  
L. Collet ◽  
D. Vinson ◽  
J. Némery ◽  
...  
Keyword(s):  
Land Use ◽  
21St Century ◽  
Surface Runoff ◽  
Groundwater Resources ◽  
Land Use Changes ◽  
Hydrological Response ◽  
Hydrograph Separation ◽  
Meteorological Forcing ◽  
The Past ◽  
Mountainous Watershed

Abstract. The hydrological response of a medium scale mountainous watershed (Mexico) is analysed over half a century. The hydrograph separation highlights an increasing surface runoff contribution since the early 1970's. This increase is attributed to land use changes while the meteorological forcing (rains) remains statistically stable over the same period. As a consequence, the intensity of annual extreme floods has tripled up over the period of survey, increasing flood risks in the region. The paper ends with a climatic projection over the 21st century. The decrease of precipitation and the increase of temperature should accentuate the trend engaged since the 1970's by reducing groundwater resources and increasing surface-runoff and associated risks.

Effects of land use changes on surface runoff

2006 ◽  
Vol 6 (1-4) ◽  
pp. 97-103 ◽  
Author(s):  
Renata Chmelová ◽  
Bořivoj Šarapatka ◽  
Přemysl Pavka
Keyword(s):  
Land Use ◽  
Surface Runoff ◽  
Land Use Changes ◽  
Effects Of Land Use

scholarly journals Analysis of Runoff Curve Number Distribution into Surface Runoff of Lesti Watershed

2021 ◽  
Vol 004 (01) ◽  
pp. 062-075
Author(s):  
Didit Priambodo ◽  
Ery Suhartanto ◽  
Sumiadi Sumiadi
Keyword(s):  
Land Use ◽  
Surface Runoff ◽  
Soil Conservation ◽  
Land Use Changes ◽  
Curve Number ◽  
Soil Conservation Service ◽  
Residential Areas ◽  
Conservation Treatment ◽  
Number Distribution ◽  
Sediment Loads

Lesti watershed is a sub basin of Brantas River located in Malang Regency, which is the main source of inflow and sediment loads for the Sengguruh Dam. Human activities change the type of land cover by deforestation for the expansion of agricultural and residential areas. It makes a rapid increasing of runoff and discharges that were potentially carrying sediment into Lesti River. To measure surface runoff in a watershed can be held by modeling rather than directly in the field, it is cheaper and more effective with accurate results. This study is based on Soil Conservation Service (SCS) formula to illustrate surface runoff level by knowing curve number distribution. Using models based on land use changes in 2010, 2012 and 2017, generated by AV SWAT software, shows that increasing CN value each year affects the surface runoff, so there is a relationship between land use and runoff. The average CN value in 2010 is 63.644, 2012 is 63.942, 2017 is 65.49, while the average surface runoff in 2010 is 800.28, 2012 is 823.26, 2017 is 828.009. Conservation treatment on the area with a high CN value can reduce the surface runoff. It shows that watershed performance is getting better

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