Hydrologic Analysis

Caption: I produced this map by selecting a pour point specific to this popular canyoneering route and analyzing the watershed to determine the size of the watershed/catchment and the associated hydrologic time of concentration. This approach is significant because flash flood risk ratings are often subjective and not based on science. I used standard ArcGIS Pro tools to delineate the watershed, including fill, flow direction, flow accumulation, and digitizing the pour point, and then ran the watershed tool. After generating the watershed, I reclassified the flow accumulation raster by classifying the values into two categories: 'Stream' and 'Not Stream' by setting a threshold of 400 or greater, where any cells with flow accumulation values above 400 were assigned to the 'Stream' class, while those below 400 were classified as 'Not Stream'. After that, I used the stream order tool to identify which canyons receive the highest flow accumulation in relation to the direct canyoneering route. In the above map, stream order one's can be found in the higher elevations of the catchment, while stream order three's are the lower and larger joined streams. Finally, I validated the results visually using NAIP and knew they were correct, as all watershed features coincided with watershed boundaries and typical stream channels. 

The analysis of the catchment area revealed several key characteristics that shed light on the terrain's topography and hydrological behavior. The slope of the catchment ranges from a minimum of 0 degrees to a maximum of 62.6 degrees, with a mean slope of 14.1 degrees. The aspect of the catchment is predominantly northwest-facing, with an average orientation of 331 degrees. The stream network within the catchment comprises three orders: first-order streams, second-order streams, and third-order streams. The percentages of stream types are: first-order streams account for approximately 60%, second-order streams make up around 22%, and third-order streams comprise approximately 18%. First-order streams are the most frequent, accounting for 17 occurrences, followed by second-order streams with 11 occurrences, and third-order streams with 8 occurrences. The total length of these streams is also notable, with first-order streams totaling 4456 meters, second-order streams reaching 1683 meters, and third-order streams extending 1320 meters. 

Stream Order Number of Streams Length (meters) Percentage of Total

First-order streams               17 4456             60% 

Second-order streams       11 1683     22% 

Third-order streams               8  1320     18%