72 D39. Surface Processes and Geomorphic Evolution, from the Coastlines to the Glaciers (Posters)

Sunday, 22 October 2017
9:00 AM - 5:30 PM
Halls 4EF

THE MORPHOLOGICAL AND SEDIMENTOLOGICAL CHARACTERISTICS OF THE SEA OF GALILEE NORTHERN DELTA, NE ISRAEL

Paper number: 72-7
Program: Technical Sessions
Time: 9:00 AM – 5:30 PM

Authors

Abstract

The drop of more than 4.5 m in the lake level of the Sea of Galilee (Lake Kinneret) in northeastern Israel due to a 4-year consecutive drought (2014-2017) and despite pumping from the lake was drastically reduced has caused deep incision of the tributaries of the Bethesda Valley into the deltaic sediments of the littoral cell. The exposure of most of the delta has also led to the complete disappearance of the vast wetland-lagoon system that characterized the area when it was inundated and loss of connectivity between the four tributary channels and their immediate floodplains. When flooded, this delta has great ecological importance (the main locality for spawning of native tilapias in the lake and nesting site for aquatic birds), but as a result of the drying up, Tamarix trees invaded the newly dried up surfaces and forced Israel Nature and Parks Authority to aggressively remove them.

The exposed deltaic sediments allowed us to conduct a thorough morphological and textural survey into areas that would otherwise be submerged and inaccessible. The results demonstrate alternating fluvial and lacustrine phases of the delta and, as expected, substantial downstream fining from the delta head towards the lake. The fluvial phases are texturally coarser while lacustrine phases are texturally finer and contain massive amounts of aquatic mollusks. We documented the distributary channels and their spatial sedimentary traits, as well as documented within-channel tilapia nests and texturally compared them to the preferred (currently dried-up) lagoon areas. The preferred areas for tilapia spawning depend on surface grain sizes, predominantly a sandy-gravelly texture. The information gathered has significant implications for future restoration and management of the delta during various lake levels and will allow defining optimal levels when both the morphological system and ecological system are least impacted during years of heavy drought. This will contribute to maintaining the Sea of Galilee northern delta, being one of the most valuable natural aquatic areas of the Rift Valley, during a period of climatic instability.

Geological Society of America Abstracts with Programs. Vol. 49, No. 6

doi: 10.1130/abs/2017AM-304053

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