Embedded Files
Questions
Attribute Queries
Q1. Which National Park Service records are classified as "National Parks"?
Q2. Which national parks have an area greater than 100,000 acres?
Spatial Queries
Q1. Which major rivers intersect national parks?
Q2. Which trails intersect major rivers within national parks?
Spatial Joins
Q1. How many national parks are intersected by a major river?
Q2. What is the total number of trails within each national park?
Combination of Queries and Joins
Q1. Among national parks greater than 100,000 acres, which park has the greatest total trail length?
Q2. Among national parks greater than 100,000 acres, which major river intersects the greatest number of parks?
Data
Study Area
The study area for this project is the contiguous United States, with Alaska and Hawaii excluded to improve map readability and maintain a consistent scale. Because the analysis focuses on National Park Service areas, the contiguous U.S. provides an appropriate geographic extent for examining their spatial relationships with major rivers and trails. This region includes a wide range of protected lands, recreation networks, and river systems, making it suitable for this spatial analysis.
Data
This project uses three GIS datasets representing National Park Service areas, National Park Service trails, and major rivers across the United States. The layers were accessed through ArcGIS Online and were drawn from government or government-affiliated sources. For consistency and readability, all datasets were clipped to the contiguous United States prior to analysis. Together, these layers support the project’s examination of spatial relationships among national parks, trail networks, and major river systems.
Name of Dataset: U.S. National Parks (DOI 2022)
Publication/Updated Date: September 22, 2022
Geometry Layer Type: Polygon
Owner: EPA Geospatial
Description: This Shared Enterprise Geodata and Services (SEGS) dataset depicts the boundaries of U.S. National Parks managed by the National Park Service (NPS). It was used to identify park units and define the protected-area boundaries for the analysis.
Name of Dataset: National Park Service Trails
Publication/Updated Date: January 15, 2026
Geometry Layer Type: Line
Owner: Esri Federal User Community
Description: This feature layer displays National Park Service trails within the United States using data from the National Park Service. It was used to examine the distribution and total length of trails within national parks.
Name of Dataset: US Major Rivers
Publication/Updated Date: January 17, 2018
Geometry Layer Type: Line
Owner: Esri Training Services
Description: This dataset represents major rivers and streams across the United States. The data were derived from sources provided by the National Weather Service and the National Operational Hydrologic Remote Sensing Center (NOHRSC). It was used to analyze how major rivers intersect national park boundaries.
Methods
All data were projected to NAD 1983 (2011) USA Contiguous Albers Equal Area Conic USGS (WKID 54096) to preserve area across the study region. An equal-area projection was necessary since this project compares the size of national parks, so maintaining accurate area measurements was important. The Albers Equal Area Conic projection is also well suited for the contiguous United States because it minimizes distortion across a large east–west extent. In addition, it is a commonly used standard for mapping and analysis in the United States.
Attribute Queries
Attribute queries were completed using the Select Layer By Attribute tool. First, the National Park Service Area Boundaries layer was queried using UNIT_TYPE = 'National Parks' to identify records classified as national parks. The selected features were exported as a new layer named 'National Parks'. Next, an Area_acres field was added to the National Parks layer and populated with the Calculate Geometry Attributes tool. A second query, Area_acres > 100000, was then used to identify parks larger than 100,000 acres. These features were exported as 'National Parks > 100,000 acres' for use in later analyses.
Spatial Queries
Spatial queries were completed using the Select Layer By Location tool. To identify major rivers that intersect national parks, the Major Rivers layer was selected based on its intersection with the National Parks layer and exported as 'Rivers intersect National Parks'. To identify trails that intersect major rivers within national parks, the Trails layer was first limited to trails located inside national parks. A second spatial query was then used to select trails that intersected major rivers. These features were exported as 'Park Trails intersect Rivers'.
Spatial Joins
Spatial joins were used to examine relationships between national parks, major rivers, and trails. All spatial joins were performed using a one-to-one join operation. To determine how many major rivers intersected each park, the Spatial Join tool was run with National Parks as the target layer and Major Rivers as the join layer, using intersection as the match option. To calculate the total number of trails within each park, the National Park Trails layer was first clipped to park boundaries. The clipped trail features were then counted within each park to calculate the total number of trails.
Combination of Queries and Joins
Combined methods were used to answer questions requiring attribute, spatial, and summary analysis. First, the National Parks > 100,000 Acres layer was used to identify large parks for further analysis. To determine which large park had the greatest total trail length, trails within those parks were clipped and summarized by park. To create a clearer interpretation of total length, a new field named 'Length_Mi' was added to convert the trail lengths from meters to miles. The Length_Mi field was used to calculate and report the total trail length for each park. For the second question, major rivers intersecting the selected parks were identified using a spatial query. The results were then summarized to determine how many large parks each river intersected, allowing comparison of rivers across the selected park subset.
Assumptions
This analysis assumes that the downloaded GIS layers accurately represent National Park Service boundaries, trails, and major rivers for the study area. It also assumes that the attribute fields used in the queries, such as UNIT_TYPE, were complete and correctly coded. For area-based analysis, park acreage values were calculated after projecting all data into an equal-area coordinate system, assuming this provided consistent area measurements across the contiguous United States.
Another assumption was that spatial relationships such as intersection reflected meaningful geographic overlap at the scale of the datasets. Because the river layer represents only major rivers, smaller streams and tributaries were not included in the analysis. Similarly, trail length calculations assumed that the trail layer was complete and that clipped trail segments within park boundaries reasonably represented the amount of trail located inside each park.
Results
Attribute Queries
Q1. Which National Parks Service records are classified as "National Parks"?
The National Park Service Area Boundaries dataset contains roughly 400 records, representing a variety of category types, including national parks, monuments, and historic sites. Of these records, 50 were classified as ‘National Parks’ within the contiguous United States. These parks are distributed across much of the study area rather than clustered in a single region, showing that the contiguous U.S. provides an appropriate geographic extent for the analysis. This query established the primary subset used in the rest of the project by separating national parks from other types of National Park Service features.
Excel Sheet: National Parks
Attribute Queries
Q2. Which national parks have an area greater than 100,000 acres?
Among the 50 national parks identified in the study area, 31 had an area greater than 100,000 acres. The 100,000-acre threshold was selected based on the median park size being approximately 170,000 acres, making it a useful cutoff for distinguishing relatively large parks while excluding smaller units. This indicates that roughly 62% of the national parks in the contiguous U.S. fall into the large-park category. The selected parks ranged in size from approximately 107,500 acres to 3,434,900 acres, demonstrating substantial variation in park area. These results show that park size differs greatly across the study region and support using a large-park subset in the combined analyses.
Excel Sheet: National Parks > 100000acres
Spatial Queries
Q1. Which major rivers intersect national parks?
Of the 24 major rivers included in this dataset, only 4 were found to intersect national parks in the contiguous United States. These rivers were the Mississippi River, Rio Grande, Colorado River, and Snake River. This indicates that direct intersections between major rivers and national park boundaries are relatively uncommon at the national scale. Even so, the rivers that do intersect parks are geographically significant and help highlight where strong hydrologic connections exist within protected landscapes. This result also suggests that although many parks may contain smaller streams or tributaries, only a limited number are crossed by rivers classified as major rivers in this dataset.
Excel Sheet: Major Rivers intersect National Parks
Spatial Queries
Q2. Which trails intersect major rivers within national parks?
The National Park Trails dataset contains more than 2,000 trail features across the contiguous United States. Of these, 97 were identified as intersecting major rivers within national parks, showing that trail-river interactions are present but relatively limited overall. However, because this analysis considered all selected trail features together, it does not identify which specific parks contain these intersections or how many occur within each park. Therefore, the result is best interpreted as a broad summary of trail-river crossings across the study area rather than a park-specific comparison. Additional analysis at the individual park level would be required to make those comparisons.
Excel Sheet: Trails intersect Rivers
Spatial Joins
Q1. How many national parks are intersected by a major river?
The spatial join analysis showed that 6 of the 50 national parks in the contiguous United States are intersected by a major river. These parks are Canyonlands National Park, Arches National Park, Grand Teton National Park, Big Bend National Park, Grand Canyon National Park, and Gateway Arch National Park. This means that only a small share of national parks have a direct spatial relationship with a major river in the dataset. However, the result also shows that the few rivers intersecting parks may pass through more than one park, creating repeated hydrologic connections across different protected areas. This pattern helps explain why only four rivers were identified in the spatial query, yet six parks were shown to be intersected in the join analysis.
Excel Sheet: National Parks intersected by Rivers
Spatial Joins
Q2. What is the total number of trails in each national park?
The total number of trail features within national parks varied widely across the study area. Counts ranged from as few as 6 trails in White Sands National Park to as many as 1,913 trails in Yellowstone National Park. These results show major differences in the amount of mapped recreational infrastructure among parks. Comparisons between park size and trail count also suggest that larger parks do not always contain more trails. For example, Death Valley National Park, the largest park in the dataset, contains only 80 trails, while Gateway Arch National Park, one of the smallest parks, contains 110. This indicates that trail quantity is influenced by factors beyond park area alone, such as development patterns, visitor use, or the way trail features are digitized in the dataset.
Excel Sheet: Trails within National Parks
Combination of Queries and Joins
Q1. Among national parks greater than 100,000 acres, which park has the greatest total trail length?
Among national parks greater than 100,000 acres, Yellowstone National Park had the greatest total trail length, with approximately 1,046 miles of trails. This total exceeded the next highest park by more than 200 miles, as the second-largest trail network measured about 842 miles. This suggests that Yellowstone is notable not only for its size, but also for the scale of its recreational infrastructure. Overall, the results show that trail length is not evenly distributed among large national parks, with some parks supporting substantially more extensive trail networks than others.
Excel Sheet: Combination 1
Combination of Queries and Joins
Q2. Among national parks greater than 100,000 acres, which major river intersects the most parks?
For the river-based combined analysis, the Colorado River intersected the greatest number of large national parks, crossing two parks larger than 100,000 acres. This made it the most spatially connected river among those included in the major rivers dataset. Although the count is small, the result still highlights the Colorado River as the strongest river-to-park link within the large-park subset. This also reinforces the broader finding that major river intersections with national parks are limited overall, but where they do occur, certain rivers play a more important role than others. At the scale of this project, the Colorado River emerged as the most prominent major river associated with large national parks.
Excel Sheet: Combination 2
Conclusion
National Park Service areas include a wide range of unit types, with about 12% of the records in the contiguous United States classified as national parks. These parks are distributed across the study area and vary substantially in size, recreational infrastructure, and interaction with major rivers. Of the 50 national parks identified in this analysis, 31 were larger than 100,000 acres, indicating that most parks in the study area cover relatively large areas.
The spatial analyses showed that direct relationships between national parks and major rivers are limited at the national scale. Only 4 of the 24 major rivers in the dataset intersected national parks, and only 6 parks were intersected by one of those rivers. This suggests that while river-park connections do exist, they are concentrated in a relatively small number of locations. Likewise, only 97 of the more than 2,000 trails were found to intersect major rivers within national parks, showing that trail-river interactions are present but relatively uncommon overall. Future analyses could incorporate tributaries and smaller streams to better represent the full range of hydrologic features within parks. A park-level analysis would also provide a more detailed understanding of how many trails intersect waterways relative to the total trail network within each individual park.
The spatial join and combined analyses further demonstrated that trail and river relationships vary considerably among parks. Trail counts ranged from 6 in White Sands National Park to 1,913 in Yellowstone National Park, revealing major differences in the amount of mapped recreational infrastructure. Among parks larger than 100,000 acres, Yellowstone had both the highest trail count and the greatest total trail length, even though it was not the largest park by area. This indicates that park size alone does not determine the amount or extent of trail infrastructure, and that each park has its own distinct spatial characteristics.
Limitations
Several limitations affect these conclusions. First, the US Major Rivers dataset includes only major rivers, which means smaller rivers, tributaries, and streams within national parks were excluded from the analysis. As a result, hydrologic connections between parks and waterways are likely underrepresented. Similarly, the trails dataset reflects mapped trail features only, so differences in data completeness or digitizing practices may influence trail counts and trail length values between parks.
Another limitation is that the study was conducted at the scale of the contiguous United States, which is useful for broad comparison but may overlook finer-scale spatial relationships within individual parks. In addition, Alaska and Hawaii were excluded to maintain map readability and scale consistency, so the results do not represent the full national park system. These limitations mean the conclusions are best interpreted as a broad regional overview rather than a complete assessment of all hydrologic and trail relationships in U.S. national parks.
References
EPA Geospatial. (2022, September 22). U.S. National Parks (DOI 2022) [Polygon feature layer]. ArcGIS Online.
Esri Federal User Community. (2026, January 15). National Park Service Trails [Line feature layer]. ArcGIS Online.
Esri Training Services. (2018, January 17). US Major Rivers [Line feature layer]. ArcGIS Online.
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