Assessing viewshed condition including scenario planning at Homestead NHP

Uden, Daniel

Homestead National Historical Park (HOME), southeast Nebraska, commemorates the 1862 Homestead Act with series of exhibits, including outdoor ecosystems that represent how the landscape may have appeared historically. The historical, scenic views of HOME have high aesthetic value but are threatened by land use changes, especially construction of tall structures visible over long distances. The impacts of development on scenic views depends on the location and height of constructed objects, topographical variability of the landscape, and the degree of visual obstruction from existing aboveground objects, such as buildings and trees. Viewshed analysis was used to estimate the impacts of development and other forms of landscape change on historic, scenic views within HOME. Two 1-meter [3.28-foot (ft)] landscape elevation datasets, a bare earth digital elevation model (DEM) and a light detection and ranging (LiDAR) digital surface model (DSM), were used to model the minimum height for aboveground object visibility in the 30-mile (mi) radius of HOME. The LiDAR-derived DSM accounted for the effects of aboveground objects on landscape visibility, while the bare earth DEM did not. Minimum height for aboveground object visibility maps were generated for four HOME observation points, based both on the bare earth DEM and LiDAR-derived DSM. Lastly, composite maps of bare earth and LiDAR-derived visibility that combine minimum height class maps across the four observation points were developed. Visibility varied across the radius, among observation points, and between elevation datasets. Despite landscape visibility generally being greater in the bare earth than LiDAR-derived viewshed maps, there was a notable degree of similarity between the bare earth composite and LiDAR-derived composite maps. Overall, visibility is greatest to the southeast and northwest, lesser to the northeast, and lowest to the southwest of HOME. Both the bare earth and LiDAR-derived composite maps indicate that aboveground objects with heights of at least 20 ft are likely to be visible from at least one of the four observation points if they are within 10 mi of HOME. Between 10 mi and 20 mi from HOME, aboveground objects with heights of at least 20–100 ft are likely to be visible if they are located north, but not south, of HOME. Between 20 mi and 30 mi from HOME, aboveground objects less than 400 ft tall are unlikely to be visible, except for small areas to the southeast and northwest. These findings can help inform future viewshed management within HOME and the surrounding landscape.

Assessing viewshed condition including scenario planning at Homestead NHP

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