Roanoke River Water-Quality Monitoring and Modeling, N.C.

Science Center Objects

The relations among river flow, floodplain water level, and instream dissolved-oxygen (DO) concentrations are important but poorly understood for the Roanoke River. Flooding and floodplain inundation no longer follow a natural seasonal pattern of flooding in the winter and occasionally in the fall, and lower flows throughout the remainder of the year, but are primarily governed by upstream reservoir releases. The objective of this study was to provide the flow and water-quality modeling tools that can be used to assess the effects of changes in John H. Kerr operations on Roanoke River flows; duration, extent, depth, and timing of floodplain inundation; DO levels in the river; and intrusion of brackish water from Albemarle Sound upstream into the river.

Background:

Map of USGS and National Weather Service data-collection sites in the Roanoke River basin, downstream from Roanoke Rapids dam

Map of USGS and National Weather Service data-collection sites in the Roanoke River basin, downstream from Roanoke Rapids dam​​​​​​​(Public domain.)

The relations among river flow, floodplain water level, and instream dissolved-oxygen (DO) concentrations are important but poorly understood for the Roanoke River. Flooding and floodplain inundation no longer follow a natural seasonal pattern of flooding in the winter and occasionally in the fall, and lower flows throughout the remainder of the year, but are primarily governed by upstream reservoir releases. The timing, duration, and extent of floodplain inundation can have either positive or negative effects on the ecosystem in the lower Roanoke River corridor, depending on the inundation characteristics. Timing, depth, and duration of floodplain inundation affects habitat use and reproductive success of wildlife and regeneration of bottomland hardwood trees.

During the relicensing process for the Roanoke Rapids and Gaston hydropower projects, studies identified potential opportunities to restore various Roanoke River habitats and mitigate effects of reservoir operations. Because operations of the John H. Kerr project primarily control overall flows in the Roanoke River, there may be a need to consider modifications in the operating rules of the project. Modeling tools, developed from extensive and credible site-specific data, are needed in order to assess effects of possible changes in Kerr operations on downstream flows, floodplain habitat, and water quality.

​​​​​​​Objectives:

The objective of this study was to provide the flow and water-quality modeling tools that can be used to assess the effects of changes in John H. Kerr operations on Roanoke River flows; duration, extent, depth, and timing of floodplain inundation; DO levels in the river; and intrusion of brackish water from Albemarle Sound upstream into the river.

Approach:

This objective will be met by performing the following tasks:

(1) review existing data and develop a hydrologic and water-quality monitoring plan to support modeling;

(2) review existing modeling frameworks for the Roanoke River;

(3) implement the hydrologic and water-quality monitoring program;

(4) develop, calibrate, and test a hydrodynamic model that is capable of simulating upstream and downstream movement of water, as well as the storage and release of water from the floodplains;

(5) develop, calibrate, and test an unsteady water-quality model that simulates DO dynamics in the main channel and the floodplain and accounts for the effects of brackish water intrusion from Albemarle Sound on flow and DO processes; and

(6) apply these models to determine effects of selected water management scenarios on downstream flows, floodplain inundation, and DO.

USGS Real-Time streamflow data for the Lower Roanoke River

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0208062765     ROANOKE RIVER AT HALIFAX, NC
02081000         ROANOKE RIVER NEAR SCOTLAND NECK, NC
02081022         ROANOKE RIVER NEAR OAK CITY, NC
02081028         ROANOKE RIVER AT HAMILTON, NC
02081054         ROANOKE RIVER AT WILLIAMSTON, NC
02081094         ROANOKE RIVER AT JAMESVILLE, NC
0208111310     CASHIE RIVER AT SR1257 NEAR WINDSOR, NC
0208114150     ROANOKE RIVER AT NC 45 NR WESTOVER, NC