Bathymetric Surveys on
Ponds 3, 4, & 5,
Napa-Sonoma Marshes
U.S. Geological Survey
John Y. Takekawa, Lacy M. Smith, & Nicole D.
Athearn
U.S. Department of the Interior
U.S. Geological Survey
Bathymetric Survey Overview

Goal: Document geomorphologic changes
that have occurred since restoration of tidal
flow
 New baseline data – Post-Breach Ponds 4 and 5
 Comparable data
 Pond 3: 2001 (Towill) vs. 2009, 2001 vs. 2005, 2005 vs.

2009
Ponds 4 & 5: 2001 (Towill) vs. 2009
 Additional mapping of original South Slough
breach, all pond breaches, and pond islands.
Bathymetry Survey Methods
RTK Antenna
Console with
laptop & RTK
Transducer
Pelican Case with Navisound
Bathymetry Survey Methods
 200 m East-West & North-South transects
Pond 3
Pond 4
Bathymetry Survey Methods

South Slough and Breaches
Pond 3 ~ 2002 South Slough Breach
 Mean elevation 2006: -3.122 ± 0.032 m (mean ± SE) NAVD 88
 Mean elevation 2009: -3.108 ± 0.031 m
2006
2009
Pond 3 ~ 2002 South Slough Breach

Net sediment gain of 46 m3 or a 1.4 cm thick layer
across the area
South Slough

Mean elevation
of South Slough
region only:
-2.85 ± 1.52 m
Pond 5 ~ Current Elevation


Mean elevation:
0.85 ± 0.003 m
(mean ± SE) NAVD 88
Elevation Range:
-1.50 to 1.53 m
Pond 5 ~ 2001 - 2009

2001: 0.78 ± 0.003 m (mean ± SE)
2009: 0.85 ± 0.003 m
Pond 5 ~ Change in Elevation

Net sediment gain:
217,625 m3

7.6 cm layer of sediment
throughout the pond
Pond 4 ~ Current Elevation

Mean elevation:
0.81 ± 0.004 m

Elevation Range:
-2.1 to 1.97 m
Pond 4 ~ 2001 - 2009

2001: 0.82 ± 0.003m (mean ± SE)
2009: 0.81 ± 0.004m
Pond 4 ~ Change in Elevation

Net sediment gain:
19,700 m3

5.4 cm layer of sediment
throughout the pond
Pond 3 ~ Current Elevation

Mean elevation:
1.05 ± 0.003 m

Elevation Range:
-1.60 to 1.90 m
Pond 3 ~ 2001 to 2009
2001: 1.17 ± 0.002 m (mean ± SE)
2009: 1.05 ± 0.003 m
Pond 3 ~ Elevation Change 2001-2009

Net sediment loss:
594,900 m3

12 cm layer of
sediment
throughout the
pond
Pond 3 ~ 2005 - 2009
2005: 0.96 ± 0.002m (mean ± SE)
2009: 1.05 ± 0.003m
Pond 3 ~ Change in Elevation 05-09

Net sediment gain:
473,800 m3

9 cm layer of
sediment
throughout
the pond
Vegetation

See Google Earth
Summary
1.4
Mean Elevation (m)
1.2
Pond 3
Pond 4
1
Pond 5
0.8
0.6
2000
2002
2004
2006
2008
2010
Future Research





Additional bathymetric surveys over time
Bathymetric survey on 9 & 10
Aerial and Ground vegetation surveys
Elevation survey of colonizing plants
Continued monitoring of bird pond use
Acknowledgements

Funding provided by USGS and CA State Coastal
Conservancy

Project support provided by: I. Woo, K. Spragens, K.
Thorne, J. Shinn, A. Brand, K. Brailsford, C. Daggett,
P. Gibson, T. Edgarian, S. Bishop, S. Piotter, K.
Hirsch, and H. Haselbach