Graduation Year

2021

Document Type

Thesis

Degree

M.S.

Degree Name

Master of Science (M.S.)

Degree Granting Department

Geology

Major Professor

Kai Rains, Ph.D.

Committee Member

Mark Rains, Ph.D.

Committee Member

Geoff Fouad, Ph.D.

Keywords

GIS Methods, National Hydrography Dataset, National Wetlands Index, Stream Order

Abstract

The seasonal expansion and contraction in a stream-wetland flow network is often difficult to characterize due to a lack of accurate mapping products, but proper characterization is important for the management of these resources. A new approach to mapping hydrography, resulting in a Regional Hydrography Dataset (RHD), may offer additional insights not provided by the national standard, the National Hydrography Dataset (NHD). The RHD can be customized to provide seasonal or monthly hydrograph, whereas the NHD is static. We conducted field validation (241 sites) and geospatial analyses to assess the accuracy of these products in the northern Tampa Bay Area. RHD was more accurate, had a lower error of omission rate, and was more representative of our study area conditions than NHD. RHD also had fewer false-negative prediction points, which means it was better at conveying the landscape connectivity we were observing on the ground. RHD is an improvement but does not substitute for wet season fieldwork when accuracy is critical. We conducted a geospatial analysis to characterize the flow network, including connected wetlands, through a year. We found that seasonality affected flowline length, which inherently affected the amount of connected wetland area. Between August and May, 37% of the wetland area connected to the stream network in the wet season is disconnected as the flow network transitions into the dry season. To determine which sections of the flow network were experiencing the most drastic changes, we used the Strahler stream ordering method for May and September hydrography. It was found that 99.7% of first-order streams, 69% of second-order streams, and 18% of third-order stream length were lost due to seasonal influences. Most seasonal flow is in 1st, 2nd, and 3rd stream order streams, while perennial occurs primarily in higher-order positions (i.e., 4th, 5th, and 6th orders)

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