FLUVIAL ISLANDS ANALYSIS: A CASE STUDY OF INDICATORS ON THE SUSQUEHANNA RIVER

Fluvial islands analyses are important to rebuild the hydrological and ecological characteristics of the river. They reveal a story through their sedimentation history, how the island was formed, and disturbance events they have experienced. In this study, two islands were selected to interpret some of the dynamic aspects of the Susquehanna River. Both islands are located 10.3 km south of the confluence of the west and north branches of the Susquehanna River and are accessible from the Isle of Que. Island 1 is located on the west side of Susquehanna River, while island 2 is on the east side. The study focuses on four indices: 1) erosional state, 2) vegetation recruitment, 3) sediment distribution, and 4) the use of indicators to determine where sediments are originating from. Three cores were extracted from each island and each core was divided into 20 cm segments. All segments were processed through a sieve test and hydrometer analysis and examined for macroinvertebrates such as Corbicula fluminea (CF). Both islands showed several disturbance events based on the sieve tests analyses. Data shows how drastically one segment can be different from another within the same core. Section 0.8-1.0 m of core 2 of island 1 showed a high uniformity coefficient (Cu) suggesting a major disturbance event while section 0.4-0.6 m of the same core reflected a low Cu indicating a low energy condition period. These types of conditions have been found in other sections in the other island. Similarly, segment 0.8-1.0 m of core 2 in island 2, showed a high Cu, while even the next section below, 1.0-1.2 m, showed a significantly lower Cu. The high density of CF at the bottom of cores 1 and 2 in island 1 with respect to the segments above raised many questions about their invasion time, recurrence and disturbances. The unexpected large amount of coal, and the absence of CF at the lower core segments made coal an indicator of island 2. Hardly any traces of coal were found on island 1. This study showed that CF is an indicator of island 1 and coal is the indicator of island 2. This ongoing study will continue to examine if these conditions persist for the other islands on both sides of Susquehanna River between Sunbury and Liverpool, PA where the flow is laminar, and the two sides stay distinguishable.