Interactions Between Rivers and Riparian Vegetation

A timeseries of aerial photographs along the Dolores River, Colorado, which has undergone over a century of hydrologic alteration, beginning with trans-basin diversions in the 1890s and followed by the construction of a large dam upstream in 1984. Vegetation changes were initially marked by expansion of tamarisk, but today most of the riparian plants are native willows, indicating differential responses to these two periods of altered hydrology.

Rivers and the riparian vegetation surrounding them present a unique bi-directional feedback: the water and sediment supply of the river influences the plants that grow along its banks, while the vegetation itself exerts a control on the form of the channel. These interactions are particularly interesting in river systems that have undergone alterations in their hydrology or sediment supply - for example, downstream from dams. As part of this research, I’m working to understand the vegetation communities that emerge following hydrologic alteration on rivers, and once established, if those vegetation communities are here to stay or if they’re dynamic in the face of a continually-changing climate or water supply.

In addition, vegetation isn’t just limited to areas along riverbanks; in-channel wood, in the form of downed logs or live plants, is vital in creating and maintaining habitat for fish and aquatic macroinvertebrates. In rivers that have undergone a history of timber harvest, the absence of in-channel wood can spell particularly bad news for habitat availability. I’ve worked on numerous projects that sought to understand the controls on in-channel wood and its availability in disturbed watersheds, particularly in the Northeastern U.S. I’m also working on research that investigates the geomorphic and ecologic effects of live, standing vegetation on fish habitat and channel geomorphology in Grand Teton National Park.

You can read about some of my recent work to uncover the links between hydrologic regimes, dam-influenced drought, and riparian vegetation response along the Dolores River in Colorado in a recent article published in EcoHydrology.

Alan Kasprak
Alan Kasprak
Assistant Professor of Geoscience

I study how rivers work, how we affect them, and the ways that we can restore their physical and ecological processes.