Assessing the Effects of EXtreme Summer Flooding on STREAM Ecosystem Successional Processes (EXSTREAM)
A NERC-funded research project led by the University of Birmingham, in collaboration with the University of Leeds
The EXSTREAM project located in Glacier Bay National Park and Preserve (GBNP) is designed to explore the resilience and vulnerability of freshwater ecosystems to summer flooding across a range of stream ages. With a view to better understand and predict the ecological impacts of future climate change, including more extreme events.
GBNP is located in southeast Alaska (58° 10’- 59° 15’N; 135° 15’- 138° 10’W), lying > 100 km west of Juneau. Glacial recession has created a deglaciated landscape with a temporal scale of 220 years across a spatial scale of 11,000 km2. The summer of 2014 has seen record-breaking prolonged high rainfall in Glacier Bay and southeast Alaska generally with the June wettest on record (189mm = 231% higher than normal). Furthermore, in July precipitation was 180% more than normal with 211mm, the second wettest July on record. Heavy precipitation continued into August with the 12thbeing the wettest August day on record. This has created a series of large and recurrent atypical flood events (Fig. 1) during the summer (some events 8x median flow).
Hydrograph of a stream near the study area
Floods are a significant natural feature of the flow regime of many rivers, and widely acknowledged to be a major force structuring stream communities. The projected increase of high-magnitude rainfall events with climate change in many regions of the world will alter the role of floods in structuring riverine habitat and their communities. However, a full understanding of the effects of extreme floods across a range of organismal groups has been hindered by the lack of long-term pre-disturbance data that would permit insights into the interaction of community dynamics, successional processes and stream channel geomorphology.
The research team is investigating the effects of summer flooding on a range of freshwater organisms (macroinvertebrates, meiofauna and fish densities). We’re also exploring how extreme high summer flows can alter river channel geomorphology and woody debris retention.
