1. Circulation characteristics of a shallow estuary plagued by water quality issues
Janelle Reynolds-Fleming and Rick Luettich
Institute of Marine Sciences
UNC-Chapel Hill
ERF Conference
September 27, 1999

2. The Neuse River Estuary, N.C.
1. Be sure to point out Morehead City
2. Point out Cape Lookout
3. Point out Minnesott Beach and the Ferry
4. Point out New Bern

3. The Neuse River Estuary Quick Facts
Drowned River Valley
Part of Albemarle-Pamlico Sound system
Average depth is ~3.6 m
Length is over 70 km
Average width is ~6.5 km
Structure varies from “well-mixed” to “highly stratified”
14,550 km watershed area
1. Mention that the Albemarle-Pamlico Sound System is the top 5 largest estuaries in North America 2

4. Water Quality Issues
Increased Residential, Industrial and Agricultural growth
Declining water quality
Outbreaks of algal blooms
Periods of hypoxia and anoxia - seasonal
Fish kills
1. Adversely affect local fishing economy as well as tourismand recreational boating.
2. In response to these issues, an effort to understand the circulation in the estuary was initiated in 1997.

5. Phase I: Questions
What are the general circulation characteristics of the Neuse River Estuary?
Influence of astronomical tide
Influence of wind
How does circulation influence stratification?
Eventually: How does circulation influence dissolved oxygen levels and the occurrence of fish kills?

6. Phase I: Circulation Study - Instrumentation
Two Moored S4s
currents
salinity
temperature
Moored water level gauge
Shipboard transects
hydrography, including D.O.

7. Phase I: Circulation Study
NEUSE RIVER ESTUARY
S4 mooring
Water level gauge
New
Transect Locations
Bern
Broad
Creek
Trent River
Arapahoe
Brice Creek
CROATAN
1. The S4 mooring was maintained from August 1997-September 1998
NATIONAL
FOREST
H148
H100
South
H120
River
Tucker
Creek
Adams N
Cherry
Creek
Slocum
South
Point
10 miles
Creek
River
Hancock
Back
Creek
Creek
10 kilometers
Clubfoot
Havelock
Creek

8. Phase I: Water Level Gauge

9. Power Spectrum for Water Level

10. Comparison with Tidal Signal

11. Coherence of Water level to wind
Coherence Level

12. Phase I: S4 Time Series

13. S4 Time Series Data estuarine riverine Anti-riverine estuarine
1. The riverine section corresponds to a time when the Kinston discharge was really low. Throughout the month of July, discharge was less than 5.00 m3*10^6.
2. The riverine section also corresponds to the time period of August 1-2. The Met data shows that it was mostly cloudy over those two days, and only two of the 48 observations show “light rain.” Leads one to believe that circulation is more directly influence by wind.
3. Notice that during the riverine period, the winds are from the NE and during the typical estuarine, the winds are from the SW.
Anti-riverine

14. Power Spectrum for velocity

15. Comparison with Tidal Signal

16. Along Channel Velocity vs. water level

17. Along Channel Coherence

18. Phase I: Shipboard Transects

19. Shipboard Transects - Alg. Channel Velocity
July 29, :29
July 29, :32
NE 5-10 kts
SW kts
-1.00
-1.00
-1.50
-1.50 ) m
-2.00
-2.00 ( c e a f s u r
-2.50
16.00
-2.50 w o b e l s ) / h m p t
-3.00 c (
-3.00 e D m a
8.00 e r t
-3.50 n s
-3.50 w o
0.00
0.50
1.50
2.50
3.50
4.50
5.00
0.00
0.50
1.50
2.50
3.50
4.50
5.00 d
July 30, :05
S 5-10 kts
S 5-10 kts
0.00
July 30, :00
-1.00 s )
-1.00 D e p t h b l o w s u r f a c ( m )
Across Channel Distance from the North Shore (km) / m c ( m
-1.50
-8.00 a e
-1.50 r t p s u
-2.00
-2.00
-16.00
-2.50
-2.50
-3.00
-3.00
-3.50
-3.50
0.00
0.50
1.50
2.50
3.50
4.50
5.00
0.00
0.50
1.50
2.50
3.50
4.50
5.00
Across Channel Distance from the North Shore (km)

20. Shipboard Transects - Acr. Channel Velocity
NE 5-10 kts
SW kts
July 29, :32
July 29, :29
-1.00
-1.00
-1.50
-1.50 ) m ( c e a f
-2.00
-2.00 u r s w o l
16.00 e
-2.50 b
-2.50 h p t e ) D s /
-3.00 m c
-3.00
8.00 ( d a r w
-3.50 h r t
-3.50
0.00
0.50
1.50
2.50
3.50
4.50
5.00 o n
0.00
0.50
1.50
2.50
3.50
4.50
5.00
0.00
July 30, :05
S 5-10 kts
S 5-10 kts
July 30, :00
-1.00 s )
-1.00
-8.00 / m c ( d
-1.50 a r
-1.50 w h ) u t m
-16.00 o ( s e c
-2.00
-2.00 a f r
-20.00 u s w o e l
-2.50
-2.50 b h p t e D
-3.00
-3.00
-3.50
-3.50
0.00
0.50
1.50
2.50
3.50
4.50
5.00
0.00
0.50
1.50
2.50
3.50
4.50
5.00
Across Channel Distance from the North Shore (km)
Across Channel Distance from the North Shore (km)

21. Shipboard Transects - Hydrography
SW kts
NE 5-10 kts
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
4.50
5.00
5.50
-4.00
-3.50
-3.00
-2.50
-2.00
-1.50
-1.00
-0.50
July 29, :00
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
4.50
5.00
5.50
-4.00
-3.50
-3.00
-2.50
-2.00
-1.50
-1.00
-0.50
July 29, :15 d i s o l v e x y g n ( m / )
0.00
2.00
4.00
6.00
8.00
10.00 m ) ( h t d e p
S 5-10 kts
S 5-10 kts
Across-channel distance from north shore [km]
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
4.50
5.00
5.50
-4.00
-3.50
-3.00
-2.50
-2.00
-1.50
-1.00
-0.50
July 30, :45
0.00
Across-channel distance from north shore [km]
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
4.50
5.00
5.50
-4.00
-3.50
-3.00
-2.50
-2.00
-1.50
-1.00
-0.50
July 30, :45 d e p t h ( m )

22. Phase I Closure: Data Interpretation
Water level influenced by wind and not astronomical tides
Circulation controlled by:
long period winds
freshwater discharge
short period wind forcing
12 hour seiching from Albemarle/Pamlico Sound
Noticeable across channel velocity variability

23. Phase II Questions
What are the major contributors to across channel circulation?
What are the driving mechanisms of the 12 hour seiching?
Can we quantify how wind direction, speed and duration influence currents?
Eventually: Does across channel circulation contribute to fish kills?

24. Phase II: Circulation Study - Instrumentation
Moored ADCP with CTD
currents for entire water column at two locations
point hydrography
Vertical Profiling CTD
hydrography for water column including D.O.
Water Level Gauge
Shipboard Transects
currents
hydrography, including D.O.

25. Phase II: Circulation Study
NEUSE RIVER ESTUARY
ADCP mooring and CTD
Water Level gauge
New
Vertical Profiler CTD
Bern
Transect Locations
Broad
Creek
Trent River
Arapahoe
Brice Creek
CROATAN
H68
1. The S4 mooring was maintained from August 1997-September 1998
NATIONAL
FOREST
H95
South
H120
River
Tucker
Creek
Adams N
Cherry
Creek
Slocum
South
Point
10 miles
Creek
River
Hancock
Back
Creek
Creek
10 kilometers
Clubfoot
Havelock
Creek

26. Phase II: Preliminary Data
Northward
Southward

27. Phase II: Preliminary Data
Downstream
Upstream

28. Conclusions Phase I Phase II will : provided general circulation data
established future questions
aided in the formation of Phase II study
Phase II will :
quantify the role of wind in across channel circulation
explain the occurrence of seiching
explain the role of circulation in fish kills