Altered hydrologic and geomorphic processes and bottomland hardwood plant communities of the lower White River Basin

Introduction

The work explained in this report was conducted to assess geomorphic adjustment of the lower White River, Arkansas, to hydrologic modifications and establish forest age and community structure within selected communities within the floodplain. Also, the HEC–GeoRAS model was evaluated for predicting flood depth and duration within the floodplain. Hydrologic modeling using HEC–GeoRAS is a common way to model flooding in a floodplain. A parameterized model exists for the White River, Arkansas, based on observed flows at gauges, but its ability to reproduce current and future hydrological conditions throughout the floodplain has not been quantified. The objectives of this work are to—

1. Identify current and historical rates of bank erosion and channel migration.  
2. Determine bank heights and channel incision along the river from Norrell lock to DeValls Bluff.
3. Determine sedimentation rates along three sections of the floodplain (as in the Clarendon area, near St. Charles, and near Jacks Bay).
4. Evaluate the accuracy of the HEC–GeoRAS model in predicting water depths in the floodplain.
5. Determine stand establishment patterns of bottomland hardwoods within selected plant communities along three sections of the floodplain.

This study provides baseline information on the current geomorphic and hydrologic conditions of the river and can assist in the interpretation of forest responses to past hydrologic and geomorphic processes. Understanding the implications for floodplain forests of geomorphic adjustment in the Lower Mississippi Alluvial Valley is key to managing the region’s valuable resources for a sustainable future.