Modeling Storm-Induced Inundation on the Yukon Kuskokwim Delta for Present and Future Climates

1. Modeling Storm-Induced Inundation on the Yukon Kuskokwim Delta for Present and Future Climates Tom Ravens and Jon Allen, Univ. of Alaska Anchorage Kashunuk R. 10 km 10 km

2. Research Goal: determine the likely change in YK Delta ecology due to storm surges – enhanced by sea level rise • Tasks: • Develop and validate a storm surge model • Identify a number of representative storms from the past 40 years • Model these storms and their inundation under present climate conditions • Re-model these storms assuming one or more sea level rise scenarios • Compute an inundation index from each model run • Compute an annual inundation index based on inundation indices from selected storms • Establish the relationship between annual index and ecological parameters (e.g., vegetation type) under present climate • Infer changes in ecological parameters (e.g., vegetation type) under a future climate based on projected changes in inundation index

3. Storm surge modeling -course grid model domain YK Delta

4. Storm surge modeling –fine scale model of YK Delta Kashunuk River Hooper Bay

5. Measured and Modeled storm surge at coast on YK Delta

6. Storms to study 1Chapman et al. Storm-Induced Water Level Prediction Study for the Western Coast of Alaska, USACE. Reported surge is for Hooper Bay. It does not include tides. 2 Calculated using ADCIRC (course grid) and DELFT3D (fine grid) models. Reported surge is for lower Kashunuk River. It does not include tides.

7. 15 year, 4 m 1 year, 2.5 m 5 year, 3.2 m

8. GMT AK time

9. 1 year storm inundation index wide view close-up [m-days] [m-days]

10. 5 year storm inundation index wide view close-up [m-days] [m-days]

11. 15 year storm inundation index wide view close-up [m-days] [m-days]

12. Annual Inundation Index for current climate based on a weighted average of indices from the 1, 5, and 15 year storm (using weights of 1, 1/5, 1/15 - approximately) Nearshore Inundation Index dominated by contribution of 1-year storm Inland Inundation Index dominated by contributions of 5 and 15-year storms [m-days/yr]

13. Correspondence between 1-2 m-day/yr annual Inundation Index and presence of Brackish Wet Sedge Meadow in current climate Brackish wet sedge meadow 1-2 m-days/yr [m-days/yr]

14. Annual Inundation Index – current climate Annual Inundation Index – future climate 1-2 m-days/yr 1-2 m-days/yr [m-days/yr] [m-days/yr] 7 km translation of 1-2 m-days/yr annual Inundation Index region – suggesting a similar shift in the location of the Brackish Wet Sedge Meadow vegetation type

15. Conclusions • Preliminary model validation efforts indicate that the model works reasonably well for 1-yr storm. • The annual inundation index was well-correlated with vegetation type. • The annual inundation index increased significantly with the assumed 0.4 m sea level rise. • Significant shifts in vegetation are expected with a 0.4 m sea level rise.

16. Future Work • Include wind and wave action in storm surge model. • Do additional model validation including use of aerial images of inundation extent to calibrate overland flow roughness. • Study additional storms and calculate return period of those storms at the Kashunuk River mouth. • Analyze the relationship between annual inundation index and vegetation type more precisely. • Examine the relationship between inundation index and bird/nest abundance. • Model and analyze pond water quality. • Model and analyze geomorphic change.

17. Collaborators and supporters • Craig Ely, John Terenzi (USGS, Alaska) • Torre Jorgenson (Ecoscience) • Raymond Chapman, Ken Eisses (USACE) • Steven Gray (USGS AK Climate Science Center) • Joel Reynolds, Karen Murphy (Western Alaska Landscape Conservation Cooperative) • Sarah Saalfeld (USFWS)

18. Questions?