Channel planform dynamics were analyzed for the River Nun; a major distributary of the River Niger from 1985 to 2015 using GIS and Remote sensing applications. Satellite imagery of the area from 1985, 1995, 2005, and 2015 were analyzed by means of GIS and used to determine the planform characteristics and changes in width, sinuosity, and shoreline migration rates. The channel planform dynamics were determined by comparing sequential changes in the position of the shorelines in these years. Sinuosity adjustments during the study were small and range between 1.74–1.76. The initial sinuosity (1.74 in 1985) increased to 1.75 in 1995 and then increased to 1.76 in 2015. Channel expansion is observed to be the dominant planform process, owing to periodic floods within the study area. The river’s channel width barely expanded from 1985 to 1995 (by 0.1 %). However, there is a constant increase in expansion within the study years that by 2005-2015 expansion had increased to 9%. The bank erosion was prevalent. Mean erosion rates ranged from 0.7 m/year in 20 years (1985-2005) to 2m/year in 30 years (1985-2015). In the 1st 10 years (1985-1995) less than 0.1 m of deposition was observed. The mean erosion rates ranged from 1.3 to 1.6 m/year on the left side and 2.8 to 3.8 m/year on the right side of the channel. Mean accretion rates of 1.2 m/year on the left side and 1.8 m/year on the right side were observed. The channel is observed to move generally towards the east (right).
This study used repeat satellite imagery and Geographic Information System analysis to assess the plan-form dynamics along the length of the lower Niger River Valley from Onitsha city to the coast between 1985 and 2015. The aim is to understand the altered dynamics and its plausible causes in this data-poor region. Analyses revealed that the Niger River has undergone change corresponding to enhanced instability in terms of an increased rate of erosion. In the study area, a change was observed from 3.7% of deposition in the first 10 years (1985–1995) to 3.9% of erosion in the next 10 years (1995–2005) and 4.7% of erosion in the last 10 years (2005–2015). Total erosion over the 30-year period (1985–2015) in the delta was calculated on 4.8%. The river channel has migrated toward the east in the upper and lower reaches while the mid-section of the channel is migrating towards the west. The east river bank is observed to be more unstable compared to west bank line through the study period. The maximum shifts identified were 3.35 km of deposition in 10 years (1985–1995), 3.31 km of erosion in the next 10 years (1995–2005), and another substantial erosional shift of 3.35 km in the next 10 years (2005–2015). Avulsion rates gradually moved from −42.1 m ∙ year−1 (1985–2005, segment F) to 100.2 m ∙ year−1 (1985–1995, segment D), large deposition in the first 10 years. Total avulsion rates of the delta in the last 30 years (1985–2015) has pointed on erosion (−2.2 m ∙ year−1). The altered dynamics observed would likely threaten the future of the frag-ile lower river system environment and raise concerns for operators with infrastructure within the Niger Delta.
Remote sensing and GIS based results from the geometric characterization of braid bar deposits in the Niger Delta are presented in this work. In this study the geometry of 67- braid bar deposits from Landsat images of 1985 and 2015 were documented and compared to determine the relationship that exist between geometric dimensions and the amount of change that has occurred on them. The braid bars identified in this work are all associated with fluvial environment in the Niger Delta. Braid bars in 1985 are observed to be greater in length, width and area than those in 2015. R² values (0.6) indicate that a significant relationship exists between braid bar length and width. R² values also indicate a significant relationship exists between both length and area (0.7) and width and area (0.8) of the braid bars values within the study area. Thus, the utilization of width to predict the length and vice versa of braid bars is reasonable. Hence data from this study provides relevant information on size ranges that can be utilized for the efficient characterization, modelling and development of hydrocarbon reservoirs.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.