Sediment and nutrient budget for assessing pollutants in floodplains in the Blue River Watershed, Kansas City, Missouri

Keywords: Nutrient budget, STEPL, Sediment budget, Floodplain
Abstract Type: Paper Abstract

Abstract

Quantifying the cycling of sediment-bound nutrients through a watershed is a complex process due to various sources and transport factors related to both historical and present-day inputs. Floodplains can function as both a nutrient sink and source and therefore can play an important role in nutrient cycling and retention in watersheds. The purpose of this study is to examine the capacity or lack thereof, for floodplains to store sediment and reduce nonpoint loadings to downstream receiving waters. This study focuses on three floodplain sites including their riparian and upland catchment areas along the Blue River in Kansas City, Missouri. Land use is agricultural in the upper watershed but is urban and suburban in the lower portion of the watershed. Contemporary floodplain sedimentation rates were measured using sediment traps and buried root dendrochronology. Bank erosion rates were calculated using ArcGIS tools to analyze bank line positions on aerial photographs from the 1990s to the present. Floodplain sediment and soil samples were collected from channel banks, levees, and backswamps and tested for organic matter, metals, Total Nitrogen, and Total Phosphorus content. Finally, the Spreadsheet Tool for the Estimation of Pollutant Load (STEPL) model was used to determine the losses and gains of sediment and nutrients by runoff based on land use, rainfall, and soil type. A sediment budget framework will be used to analyze sediment and nutrient storage in floodplains in comparison to annual stream loads.