The Ecological Significance of Emerging Deltas in Regulated Rivers

Sedimentary deltas forming in the world’s regulated rivers are a glaring gap in our knowledge of dammed riverine ecosystems. Basic ecological information is needed to inform the current debate about whether deltas should be retained and managed to gain ecosystem services lost under reservoirs or whether they should be partially removed to improve flow conveyance and to resupply sediment-starved reaches below dams. An examination of nine deltas on the heavily regulated upper and middle Missouri River showed the following: The sizes, dynamics, and biotic communities vary widely across deltas; riparian forest has established on portions of most deltas; the current delta area is over 1000 square kilometers, exceeding forest area in remnant unimpounded reaches and offering considerable land area for restoration actions; and small adjustments to reservoir operations could improve the restoration potential of deltas. Ecological studies are urgently needed to determine the future role that deltas could play in river ecosystem restoration

The Dammed Missouri: Prospects for Recovering Lewis and Clark\u27s River

The world’s dams and reservoirs are aging. The ecological effects of a half-century or more of flow regulation and sediment alteration are becoming apparent. What remains of the highly dynamic channel and riparian ecosystem of the Missouri River described by Lewis and Clark has become static. Recent long-term studies have determined that some of the impacts on the Missouri River ecosystem turned out as predicted, such as the failure of cottonwood-dominated riparian forests to successfully establish and survive on a broad scale. Other changes were surprises, such as the effect of disease eliminating a formerly dominant tree species and the appearance of mainstem and tributary deltas affecting channel slope, floodplain hydrology, and vegetation. Restoration of the river’s hydrologic and sediment regime has been delayed long enough that the chances of functional ecosystem restoration have been greatly reduced and complicated. Two phases are now needed to attempt to restore the riparian ecosystem: one to repair the effects of post-dam changes (channel incision, bank stabilization) and another to reestablish pre-dam flow and sediment regimes. The prospects for restoration of this valuable ecosystem, rich in history and in goods and services provided to the public, are dim. Time has diminished the chances that restoration or even rehabilitation can be achieved

Lake-Francis-Case-Water-Surface-Elevation-1989-2013

Water Surface Elevations of Lake Francis Case, 1989-2013. Data were derived from the US Geological Survey Gage 06442996 at Chamberlain, South Dakota. A README file is provided on the first worksheet

README-Methods-for-vegetation-data-summarization-analysis

A description of the methods used to summarize and analyze vegetation composition and structure

Delta-backwater-Missouri-River-species-presence-comparison

Woody species presence on the White River delta-backwater and the Garrison and Gavins Point remnant reaches of the Missouri River. A README file is provided on the first worksheet

Stand-locations-and-boundaries-shapefile

An ArcMap shapefile with all stand sampling locations and boundaries

GIS-woodland-age-area-distribution-by-year

Riparian woodland age-area distribution by year on the White River delta-backwater, based on GIS analysis of historic aerial photos. A README file is provided on the first worksheet

Overstory-species-composition-structure

Overstory tree species composition and structure across the study site. A README file is provided on the first worksheet

Liana-presence-absence

Liana (woody vine) species presence/absence in sampled stands. A README file is provided on the first worksheet

Cottonwood-and-willow-seedling-sapling-density

Density values for cottonwood and willow seedlings and saplings in each sampled stand. A README file is provided on the first worksheet