Nielsen Dam A, also known as Cross Dike, is a privately owned earth dam located in Bothell, Washington. Completed in 1950, this dam serves primarily for recreational purposes along the Tr-Sammamish River. With a hydraulic height of 15 feet and a storage capacity of 73 acre-feet, it offers a serene setting for water resource and climate enthusiasts to enjoy outdoor activities in Snohomish County.

Managed and regulated by the Washington Department of Ecology, Nielsen Dam A has been deemed to have a low hazard potential and is currently in a not-rated condition assessment. Despite its age, the dam continues to provide a safe and enjoyable environment for visitors, with a normal storage capacity of 45 acre-feet and a maximum discharge rate of 16 cubic feet per second. Its location in the scenic surroundings of the Sammamish River watershed adds to its appeal as a recreational destination for locals and tourists alike.

While there is limited data available on the structural details and maintenance history of Nielsen Dam A, its presence contributes to the overall water management and conservation efforts in the region. With its proximity to the Sammamish River and the diverse flora and fauna that thrive in the area, this dam serves as a vital component of the local ecosystem and a valuable resource for those interested in water resource management and climate resilience.