## 1 Introduction  
Stream burial--the routing of streams through culverts, pipes, and concrete lined channels, or simply paving them over--is common in urbanized areas [1; 2; 3; 4; 5]. In many regions, the majority of buried reaches are headwater (1 st and 2 nd order) streams, including ephemeral and intermittent reaches, with removal of up to 70% of headwater stream length in some areas [1; 3]. While the cumulative effects to ecosystem processes wrought by stream burial have important ramifications for regulation under the U.S. Clean Water Act [6], the extent of burial has not been assessed for most urban areas. Knowledge of the extent of burial events is critical for effective resource management, including preservation of remaining intact streams, restoration of urban streams, and assessing cumulative impacts of urbanization to water quantity and quality. As with other forms of stream modification, burial alters the primary physical, chemical, and biological processes in headwater systems, contributing to a state of degradation commonly referred to as \"urban stream syndrome\" [7]. With the percentage of the world's population living in urban areas continuing to grow [8], a greater emphasis has been placed on understanding the structure and function of urban streams, and associated impacts to human health, and that of downstream ecosystems. The identification of stream burial as a critical and pervasive driver of the \"urban stream syndrome\" [7], and the recognition that key questions remain in regards to ecosystem structure and function within piped ecosystems [9], has led to increased research activity, and the explicit consideration of stream burial in formulation of long-term research agendas (e.g., the Baltimore Long Term Ecological Research (LTER) site; [PERSON], _personal communication_). Subsequent attention has focused on extensive stream burial as a key contributor to \"urban stream deserts\" [4], riverless urban areas that evolved primarily due to stream burial for human development and population growth [10], and the phenomenon of convergent surface water distributions across urban areas of the United States [11], whereby there is a decrease in variance in the density of surface flow channels--streams and rivers--with increasing development intensity, largely due to burial of stream channels. While not extensive to date, studies of stream burial have demonstrated a consistent set of interrelated ecosystem impacts, including modified flow velocities, altered carbon and nutrient inputs, and amplified nitrogen transport [9], loss of habitat and decreased nutrient subsidies [12], and barriers to dispersal of aquatic organisms [13]. More recently, [PERSON] and [PERSON] [14] have recognized stream burial as part of an \"urban stream continuum\", whereby extensive engineering of headwater systems has expanded natural flowpaths (\"urban karst\"), leading to increased hydrologic connectivity within watersheds, thereby influencing the flux and transformation of nutrients, contaminants, and energy across both space and time. Leveraging this novel conceptual framework, subsequent research has focused largely on biogeochemical cycles within buried headwater streams, documenting significant reductions in nitrogen (N) uptake, gross primary production (GPP), and ecosystem metabolism (ER), with potential to influence watershed nutrient exports to downstream waters [15; 16; 17]. Research has demonstrated a consistent negative effect of increasing levels of urbanization on various indicators of stream health [7; 18; 19]. Most studies have relied on total imperviousness (TI; the proportion of a watershed that is covered in impervious surface) as the primary measure of urbanization impacts on freshwater ecosystems as TI is viewed as an integrative and comprehensive indicator [20] that can be readily incorporated into land use planning [12; 21; 22].