The savannah formations known in this part of the country are:

- Acacia hockii savannah and Dicrostachys cinerea subsp. africana. At the level of Lower Rusizi, formerly cultivated areas are currently invaded by Acacia hockii with grass stands formed by Hyparrhenia; - Savannas with Sporobolus pyramidalis and Balanites aegyptica.
They are located in the Rusizi National Park. They line the weak depressions of the lake plain where they are subject to temporary flooding during rainy periods;

- Grassy savannah with Phragmites mauritianus. In the Rusizi Delta, a savannah with Phragmites mauritianus clearly dominates. This reed vegetation contains shrubs such as Securinega virosa, Pluchea ovalis, Vernonia amygdalina, forming thickets enriched with voluble herbs such as Cynanchum schistoglessum, Ipomea cairica, Cissampelos micronata, etc... The undergrowth consists of Asystagia gangetica, Achyranthes aspera, etc.;

- Acacia polycantha var. campylacantha tree savanna. At the mouth of the Rusizi Delta, this savannah occupies the sandy soil where Acacia polyacanthavar. campylacantha emerges in a grass mass with Phragmites mauritianus. The dominant stratum of about 20 m is occupied by Acacia polyacantha. The dominated, not well differentiated stratum consists of Rhus longipes, Hoslundia opposita, Securinega virosa, embedded in a grass carpet.