Multi-Temporal Analysis of Avulsion and Channel Dynamics: A Case Study of the New Channel in the Kwando River, Botswana

Abstract

Channel modifications and avulsions through time and space have a big impact on how streams flow and
how wetlands develop. The objective of this study is to identify the factors that cause the Kwando channel
to avulse in Botswana territory and to explain the spatiotemporal sequences that accompany this move
ment. The study, which was conducted in 2016, used Garmin-GPSMap 62S to collect the coordinates
of the split New Channel from the trans-boundary Kwando River’s west bank. By looking through the
Google Earth photographs from 1985 to 2017 on a desktop computer with the selected images from July
1985, May 2002, December 2011, December 2013, and December 2017, the multi-temporal fluctuations
in the New Channel spatial position are given and discussed. The map was created using ArcMap GIS 10.2
relying on field-tracked coordinates that are comparable to the well-defined New Channel for approxi
mately 45km. The formation of the New Channel might be linked to three factors: i) 547mm of above
average rainfall between 2004 and 2015; ii) increased inflows into the Kwando River between 2008 and
2015, and iii) the presence of paleochannels and flood plain sloughs in the system. According to analyses
of historical Kwando River flow data series, 51% of inflows in 1986–1994 travelled to Shummamorei sta
tion whereas 53% of inflows in 2017–2020 went to James Camp station on the New Channel, indicating
that a sizeable portion of Kwando River flows were diverted to the New Channel. Between 1995 and 2010,
channel blocks and aggravation forced the flow to be diverted to the Linyanti Swamp by bank spill, which
disrupted the flow pattern at Shummamorei. The New Channel has an impact on the outflow rivers, Savuti
and Selinda Canal. The New Channel is concentrated on downstream wetlands in Botswana and might
have an impact on the Linyanti Swamp region in Namibia.