Bathymetric Survey of Assawoman Bay, St. Martin River, Sinepuxent Bay and Newport Bay

Department of Natural Resources MARYLAND GEOLOGICAL SURVEY Emery T. Cleaves, Director

COASTAL AND ESTUARINE GEOLOGY FILE REPORT NO. 01-2

by Darlene V. Wells and Richard A. Ortt, Jr.

Submitted to

Fisheries Services Department of Natural Resources

in fulfillment of Contract #AR-00-020

Draft June 2001 Bathymetric Survey of Assawoman Bay, St. Martin River, Sinepuxent Bay and Newport Bay

Executive Summary

The Maryland Geological Survey, under contract with Fisheries Service, Maryland Department of Natural Resource, conducted hydrographic surveys in Assawoman Bay, St. Martin River, Sinepuxent Bay and Newport Bay. The purpose of the study was to provide a consistent bathymetry data set that may be used in other scientific studies. The hydrographic surveys were collected in May and June 2000, using differential global positioning service (DGPS) techniques and digital dual-frequency echo sounding equipment. Hydrographic survey lines were spaced 200 meters apart and extended from shore to shore. Five hundred kilometers of hydrographic records were surveyed and over 500,000 discrete soundings were recorded. In addition to the hydrographic surveys, water level data were collected at 10 different sites within the study area. The water level data were used to correct the echo sounding data for tide and wind offsets.

Sounding depths were adjusted to North America Vertical Datum of 1988 (NAVD88) and are listed in ASCII XYZ (northing, easting, depth) format. Location coordinates are in UTM, NAD83. The adjusted sounding data were used to generate 10-meter, regularly spaced grids for the four sub-basin areas and bathymetry (depth contour) map were created from the gridded data. The XYZ data, metadata, and maps are presented on CD-ROM.

Table of Contents

Introduction...... 1 Previous bathymetric surveys ...... 2 Study area...... 3 Methods...... 5 Study approach...... 5 Hydrographic surveys ...... 6 Depth determinations ...... 6 Horizontal positioning ...... 9 Data recording...... 9 Water level measurements ...... 10 Elevation determinations of water level recorders...... 14 Water level data reduction and tide analyses...... 15 Hydrographic survey data processing...... 15 Depth data filtering ...... 15 Sounding depth adjustments ...... 15 Gridding techniques for bathymetry model...... 17 Data accuracy...... 17 Discussion...... 17 Bathymetric grid ...... 17 Overview of the bathymetry of the northern Coastal Bays...... 17 Tides...... 18 Applications of bathymetry and tide data ...... 21 Recommendations for future work ...... 21 Acknowledgments...... 21 References cited ...... 23 Appendices A. QA/QC ...... A1 1. Echosounder depth calibration...... A1 2. Elevation determinations of water level sensors-Vertical control...... A3 3. Post-Processing Data- GPS Surveys ...... A17 B. Knudsen operating parameter settings ...... B1 C. MathCAD splining process for interpolating water level adjustment ...... C1 D. Final XYZ sounding data on CD ...... D1

iii List of Figures

Page Figure 1. Study area...... 4 Figure 2. Track lines for hydrographic surveys collected north of Ocean City Inlet...... 7 Figure 3. Track lines for hydrographic surveys collected south of Ocean City Inlet...... 8 Figure 4. Example of echogram produced by Knudsen software ...... 10 Figure 5. Locations of water level recorders and tide gauges used in this study...... 12 Figure 6. The graph showing the change in tide range and tidal phase progression (time lag) with distance from Ocean City Inlet (Marsh Harbor)...... 16 Figure 7. Plots of water levels from recorders in Sinepuxent Bay...... 19

List of Tables

Table 1. NOAA hydrographic data summary...... 2 Table 2. IHO Classification of Surveys (IHO,1998) ...... 5 Table 3. Information on water level recorders and tide stations used in this study...... 13 Table 4. Comparison of tide station mean water levels (MWL) elevations in NAVD88 determined by GPS and traditional differential leveling...... 14 Table 5. Comparison of preliminary tide datums for water level recorders operated in Assawoman and Isle of Wight Bays ...... 20 Table 6. Comparison of preliminary tide datums for water level recorders operated in Sinepuxent Bay...... 20 Table 7. Regression analysis of calibration data for Knudsen echosounder...... A1 Table 8. Elevation leveling data for the water level recorder installed on a private bulkhead in Keenwick Community, in Delaware ...... A3 Table 9. Elevation leveling data for the water level recorder installed on the Ocean City Recreation Pier (125th Street, Ocean City) ...... A4 Table 10. Elevation leveling data for the water level recorder installed on steel bulkhead, southeast point of Isle of Wight ...... A5 Table 11. Elevation leveling data for the water level recorder installed on piling at the Hudson Boat Marina (Holiday Harbor) in St. Martin River ...... A6 Table 12. Elevation leveling data for the water level recorder installed private bulkhead in Bayshore Estates in Ocean City (~27th Street)...... A7 Table 13. Elevation leveling data for the water level recorder installed on the community pier in Marsh Harbor Marina...... A8 Table 14. Elevation leveling data for water level recorder installed on a private bulkhead in Snug Harbor ...... A9 Table 15. Elevation leveling data for the water level recorder installed on the Rum Point community dock in Sinepuxent Bay...... A10 Table 16. Elevation leveling data for the water level recorder installed on the bulkhead at the South Point boat ramp ...... A11 Table 17. Elevation leveling data for the water level recorder installed on a private dock Newport Bay...... A12 iv Page

Table 18. National Geodetic Survey vertical control bench marks used as check points during GPS surveys ...... A13 Table 19. GPS post processing statistics for survey data collected during the week of 10/2/00 by Richard Ortt, Jr. and Harold Catlett...... A16 Table 20. GPS post processing statistics for survey data collected during the week of 10/2/00 by Richard Ortt, Jr. and Harold Catlett...... A18 Table 21. Knudsen echosounder system control settings ...... B1

List of Plates

Plate 1. Assawoman Bay and St. Martin River Bathymetry Map ...... Separate Plate 2. Sinepuxent Bay Bathymetry Map...... Separate Plate 3 Newport Bay Bathymetry Map...... Separate

v Bathymetric Survey of Assawoman Bay, St. Martin River, Sinepuxent Bay and Newport Bay

Introduction

The coastal bays of Maryland are environmentally sensitive areas that deserve the efforts and studies of the scientific community. Currently these studies are being performed without the current knowledge of the bathymetric framework of the water bodies. Hydrographic surveying determines the depths of the water from which a bathymetric model may be created. This model can serve as an integrating factor for various other studies and monitoring efforts such as sedimentation and sediment budget studies, sub-aquatic vegetation surveys and monitoring, water quality and pollutant transport modeling, and aquatic habitat studies. The bathymetric model also can be useful guide in the management of navigation channels and boating activities.

Recently, the State Water Use Workgroup implemented a new set of management guidelines for Maryland’s coastal bays. These new water use management guidelines, which differ from those of the Chesapeake Bay, will facilitate fulfillment of a number of goals outlined in A Comprehensive Conservation and Management Plan for Maryland’s Coastal Bays (MCBP, 1999). With the implementation of the management plan, the need for better, up-to-date bathymetric data has been identified. Certain areas within the coastal bays have been given higher priority for bathymetric studies, based on several criteria including the lack of existing bathymetric data, level of recreational activity, dredging needs, and presence of sensitive habitats. These areas include Assawoman Bay, St. Martin River, Isle of Wight Bay, Sinepuxent Bay and Newport Bay.

Detailed (first or second order surveys) bathymetric data are available for the navigation channels and the vicinity of the Ocean City Inlet. However, detailed bathymetry does not exist elsewhere in the bays. The bays are very shallow making hydrographic surveys very difficult and expensive to conduct. Because commercial navigation is not a major concern in most areas of the bays, neither the National Oceanic and Atmospheric Administration (NOAA) nor the U.S. Army Corps of Engineers have conducted hydrographic surveys in these areas.

Purpose

In response to the need for more complete and up-to-date bathymetric data in the coastal bays, the Resource Assessment Service, Maryland Geological Survey conducted hydrographic surveys in Assawoman Bay, St. Martin River, Sinepuxent Bay, and Newport Bay, using standard digital bathymetric methods (IHO, 1998; NOAA (draft)). The objectives for this survey were to: 1. Provide current, consistent, and systematic hydrographic coverage of the study areas; 2. Develop a baseline digital bathymetric data set that may be expanded and/or used for comparison with surveys conducted in the future; and 3. Provide a digital bathymetric data set applicable for model development for various

1 purposes such as circulation models, and water quality models.

This study does not include Isle of Wight Bay. At the same time we conducted the surveys for this study, the U.S. Army Corps of Engineers, Baltimore District, collected hydrographic surveys in the Isle of Wight Bay area, from the Ocean City Inlet north to Rt. 90 Bridge, as part of a project to resurvey the inlet and federal channel. The task of incorporating the Corps’ data and producing bathymetric maps of the Isle of Wight area was not included in this study.

Previous Bathymetric Studies

A listing of historical hydrographic surveys conducted by NOAA’s National Ocean Service (NOS) in Maryland’s coastal bays is given in Table 1. These surveys, using several different sounding methods and datums, represent the extent of NOAA bathymetric data available in the coastal bays. The line spacings of the NOAA surveys are approximately 1000 meters apart, providing only very general coverage of the coastal bay bottom. The data from these surveys are included in NOAA’s GEODAS database http://www.ngdc.noaa.gov/mgg/gdas/).

Table 1. NOAA hydrographic data summary. NGDC # Survey Date* Area Datum Sounding # of Method Soundings Horizontal Vertical + 03581004 H05714 12/79 Pope Is. to NAD27 MLW Lead line 11543 Chincoteague assumed Inlet 03F12118 H09715 12/79 Sinepuxent Bay NAD27 MLW Digital 1866 and Ocean City echosounder assumed 03NG1001 H01455A 12/94 Chincoteague NAD27 MLW Lead line 7040 Bay, lower parts assumed 03NG1107 H01455B 6/94 Chincoteague NAD27 MLW Lead line 3583 Bay, upper parts assumed 03NG1109 H01816 06/94 Millers Creek, NAD MLW Lead line 2278 DE to 1913 assumed Sinepuxent Bay, MD * Date when data was added to database. Surveys were conducted prior to that date but date was not given in database. + Tidal epoch was not given in NOAA summary of database.

The U.S. Army Corps of Engineers routinely conducts hydrographic surveys for the purpose of maintaining the Federal navigation channels in Isle of Wight and Sinepuxent Bays and in the vicinity of the Ocean City Inlet. These surveys are usually conducted prior to maintenance dredging and often they are limited to the areas in the vicinity of navigation channels to be dredged. The most up-to-date bathymetric data collected by the Corps focus on 2 the Inlet and ebb shoal area located on the ocean side of the Inlet. These data were collected as part of the Ocean City and Vicinity Water Resource Feasibility Study (U.S. Army Corps of Eng., 1998).

Study Area

The Maryland coastal bays are located on the Atlantic coast of the Delmarva Peninsula (Figure 1). Fenwick and Assateague Islands separate the coastal bays from the Atlantic Ocean. The Maryland coastal bays are microtidal (less than 2 meter tidal range) coastal lagoons. The two northern bays, Isle of Wight and Assawoman Bays, are distinct from the other bays in that they lie north of Sinepuxent Neck and Ocean City Inlet. These two northern bays are contiguous with each other. In this study, the Rt. 90 bridge is used as the boundary separating Isle of Wight Bay from Assawoman Bay and St. Martin River. The southern coastal bays include Sinepuxent, Newport and Chincoteague Bays. Sinepuxent Bay extends from the Ocean City Inlet, south to South Point located at the end of Sinepuxent Neck. Newport Bay is a flooded extension of Trappe Creek, which is one of the more significant streams feeding into Maryland coastal bays. Sinepuxent Neck separates Newport Bay from Sinepuxent Bay. Both Sinepuxent and Newport Bays are contiguous with Chincoteague Bay at their southern boundary.

The coastal bays are connected to the Atlantic Ocean through two outlets: Ocean City Inlet located at the northern end of Sinepuxent Bay; and Chincoteague Inlet in Virginia to the south. At the northern end of Assawoman Bay, a canal, known as "The Ditch”, connects Assawoman Bay to Little Assawoman Bay (in Delaware).

Ocean City Inlet formed during a hurricane in 1933 and was immediately stabilized with jetties to keep it open. This stabilization resulted in immediate changes in the shoreline configuration south (downdrift) of the inlet. The jetties interrupted the longshore transport of sand, essentially starving northern Assateague Island of sand. Since 1933, the northern 10 kilometers of the island have experienced an accelerated rate of erosion. Northern Assateague Island and Sinepuxent Bay have undergone dramatic changes as a result. Although island width has been maintained by overwash processes (Leatherman, 1979), portions of Assateague Island have migrated landward, as much as 350 meters along the northern-most 2 kilometers. As a consequence of this migration, Sinepuxent Bay has narrowed significantly with the surface water area of the Bay decreasing by 17% since 1943 (Wells ant others, 1996). ` Circulation patterns and tidal ranges in the northern coastal bays are dependent on proximity to Ocean City Inlet and wind conditions. Near the inlet, currents are primarily an effect of tidal cycles. Currents over 200 cm/sec are common near the inlet and within the Federal Navigation channel (Dean and others, 1978). Tidal amplitudes, based on data from NOS tide stations located in southern Isle of Wight Bay, range from 0.55 to 0.78 m. Casey and Wesche (1981) measured tidal amplitudes and current velocities at several locations in Isle of Wight and Assawoman Bays. Nominal tidal amplitudes ranged from 0.25 m on a spring tide to 0.16 m during a neap tide at the northern most station, located at Drum Pt. north of the Rt. 90 Bridge. The Ditch allows some water exchange between Assawoman Bay and Little Assawoman Bay in

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Figure 1. Study area. Sub-basins included in this study are outlined in red. Isle of Wight Bay was surveyed by the U.S. Army Corps of Engineers.

4 Delaware. Tidal amplitudes in the Ditch range from 0.6 to 0.9 m (Allison, 1975). Tidal influence diminishes rapidly with increasing distance from the inlet. For a large portion of the study area, wind conditions often have a greater effect than tides on water levels.

Methods

Study Approach

Obtaining quality bathymetric data for the Maryland coastal bays is an enormous challenge, for several reasons. First, the bays are very shallow. This shallowness creates navigational difficulties during hydrographic surveys, and has the potential to enhance any error in the sounding data. The second reason why it is difficult to obtain good bathymetric data is related to the tidal characteristics of Maryland’s coastal bays. Due to restricted access to the open ocean, the tidal range within the bays varies dramatically depending on proximity to the inlet. For most areas in the bays, water level fluctuations are often more wind-driven rather than tidally induced. Water levels cannot be predicted and have to be measured at same time and in the immediate vicinity of the hydrographic surveys.

Table 2. IHO Classification of Surveys (IHO,1998) Order Special 1 2 3 Examples of Typical Harbors, berthing areas, Harbors, harbor approach Areas not described in Offshore areas not Areas critical channels with channels, some coastal Special Order and Order described in Special minimum under-keel areas with depths up to 1, or areas up to 200m Order or Orders 1 and 2. clearances 100m depth Horizontal Accuracy 2m 5m + 5% of Depth 20m +5% of Depth 150m +5% of Depth (95% confidence level) Depth Accuracy for 0.25m 0.5m +1% of Depth 1.0m + 2% Depth 1.0m + 2% Depth Reduced Depths (95% Confidence Level) 100% Bottom Search Compulsory Required in select Areas May be required in select Not required areas System Detection Cubic features >1m Cubic features > 2m in Same as Order 1 N / A Capability depths up to 40m 10% of depth beyond 40m Maximum Line Spacing Not applicable, as 100% 3x average depth or 25m, 3-4x average depth or 4 x average depth search is compulsory whichever is greater 200m, whichever is greater

The number of transects and spacing required for hydrographic surveys depends on the techniques used and the level of coverage desired. Hydrographic surveys are traditionally associated with navigation. Due to the need to have thorough coverage for safety of ship passage and for the safety of the environment, several classifications have been created. Table 2 outlines these various classifications (IHO, 1998). First order hydrographic surveys require 100% coverage of the bay bottom, which is almost impossible to attain given the shallow depths found in the coastal bays. Since navigation was not the primary purpose for obtaining bathymetric data for most of the Maryland coastal bays, we conducted surveys at a track line spacing of 200 meters, a coverage we considered to be adequate to develop a preliminary bathymetric 5 framework for the northern coastal bays.

This study was conducted in two phases. The first was the collection of field data which consisted of three tasks: 1) conducting hydrographic surveys to obtain a systematic grid of discrete soundings in x, y, z format (geographic location and water depths); 2) installing and operating water level recorder to record water level (tide) data needed to adjust sounding data to a common datum; and 3) determining elevations (referenced to a common datum) of the water level recorders. The second phase involved the reduction and adjustment of the data to produce a bathymetric data set.

Hydrographic Surveys

Hydrographic surveys of the study area were collected using a 17 ft Boston Whaler equipped with a 70 horsepower outboard engine. Track lines followed predetermined UTM northing gridlines or easting gridlines, which facilitated navigation of the survey vessel and allowed survey lines to be easily retraced for quality control and quality assurance (QA/QC) purposes and for future surveys. Track lines were spaced 200 meters apart and extended from shore to shore (generally east-west). Tie-in track lines, used primarily for QA/QC reasons, were run every 1000 meters perpendicular to the shore to shore tracks lines. For each basin, perimeter surveys, following the shoreline, were also conducted to establish boundary (near-shore) conditions. Figures 2 and 3 show the track lines for the study area north of Ocean City Inlet and south of the Inlet, respectively. All surveys were conducted between May 1 and June 28, 2000.

Depth determinations

A Knudsen 320 B/P series marine echosounder, which transmits a dual frequency pulse signal, was used to determine depths. Frequencies of 200 kHz and 28 kHz were used for this study. The Knudsen 320 B/P echosounder determines the depth of the water by transmitting brief acoustic pulses toward the bay or ocean bottom, and measuring the time it takes for the bottom echo or reflection to return. The transducer, used for both transmitting the pulse and receiving the echo signal, was mounted off the port side of the whaler, slightly aft of the vessel’s center. The transmitted pulse of sound is of a specified frequency (in this case, two different frequencies). The intensity of the returned signal versus depth is recorded by the echosounder and displayed visually on a graph. After many repeated pulses the bay bottom becomes discernable as a horizontal black line, which follows the contours of the bottom. The sharpness and clarity of the line is a function of the strength and quality of the echo, and depends on many factors, including bottom characteristics (roughness, sediment type), pulse length, depth of the water, and the amount of ambient noise (other factors that interfere with the return signal such as air bubbles in water column, fish, changes in temperature and/or salinity). The strongest echo is identified by the Knudsen echosounder and displayed/recorded as a depth in meters. Identification involves several processes: location of the precise leading edge of the returned echo, computation of the depth based on travel time and sound speed considerations, and the determination as to whether the result represents a valid depth measurement (it might be a fish,

6 4257000 Assawoman Bay and St. Martin River

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Figure 2. Track lines for hydrographic surveys collected north of Ocean City Inlet.

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Figure 3. Track lines for hydrographic surveys collected south of Ocean City Inlet.

8 or transducer ringing, or reverberation, or just noise, or even the second echo from the previous ping) (Knudsen Engineering Limited, 1999).

Acoustic echoes are generated as a result of the sound pulses reflecting or bouncing off the density gradient separating substances of low density (such as water) and higher density (sediment or thick vegetation). Pulse characteristics such as frequency will determine how easily the sound pulse may penetrate higher density substances and what gradient level will produce an echo. For example, low frequency (28 kHz) sound penetrates soft sediments or SAV more readily than high frequency (200 kHz) signals. As a result, a two-channel echosounder will detect the shallowest interface, such as the top of the SAV bed, on the high frequency channel, and a deeper layer such as the real (sandy) bottom on the low frequency. In the case of soft sediments such as mud in-fill within a navigation channel, the echosounder will detect the shallower interface (top of the muddy sediments) on the high frequency, and the deeper channel bottom with the low frequency.

A dual frequency echosounder was used for several reasons. The use of dual frequencies allowed the penetration of thick submerged aquatic vegetation (SAV) beds to confirm the sediment-water interface (i.e, sediment surface). Also, a dual frequency echosounder can provide addition information about the characteristics of the bottom as well as sub-bottom structure. Other studies have shown tht the 200 kHz echosounder by itself may detect the top of the SAVbeds as the sediment surface.

Horizontal positioning

To determine horizontal position, an Ashtech Reliance Sub-Meter SCA-12 L1 code and carrier GPS unit interfaced to a Starlink MRB-2 DGPS receiver was used. Interfaced to the Knudsen echosounder, the Ashtech GPS system provided both position and time (date, time of day) data for depth readings. The Ashtech unit was programmed to output location coordinates only if the following criteria were met: 1) position derived from at least six satellites with positions of 15 ° or greater above the horizon; 2) Position dilution of precision (PDOP) less than 5; and 3) DGPS signal less than 30 seconds old. The Starlink DGPS tracked the signals from Cape Henry, Virginia, and Cape Henlopen, Delaware. The receiver sent updates to the Ashtech based upon the station with the strongest signal. The position latency, or time lag between the position update and the posted time of day (time of depth sounding), also was recorded. A second GPS system, a Lowrance GlobalNav 212 GPS interfaced with a Lowrance DGPS Beacon receiver was used for navigating the whaler during the hydrographic surveys.

Data recording

A laptop computer with Windows Online SCSI Echo Control Software, D40-02382, Echo Control.exe (Knudsen Engineering Limited (KEL), 1999) was used to control operating parameters, to synchronize the GPS with the echosounder, and to record data from echosounder via the sounder’s SCSI (Small Computer System Interface) port. The parameters settings used are presented in Table 21 (Appendix II). Date, time, high frequency (HF) depth, HF depth valid

9 flag, low frequency (LF) depth, LF depth valid flag, sound speed used, position (latitude and longitude), and position latency were output as ASCII comma-delimited text files (kea files). Horizontal position was recorded in Latitude and Longitude, using the North American Datum of 1983 (NAD83). HF and LF depths reflecting the distance from transducer to either the water- sediment interface (bay bottom) or sub-bottom interface were recorded in meters. The HF and LF depth flags and position latency were used to filter out “bad” data (See discussion under Depth data filtering). Because the GPS updated location every second while the Knudsen recorded a depth sounding every 0.5 seconds, there are two depth soundings for every unique location coordinate pair.

The Knudsen software permitted the display, in real-time, of a gray-scale graphic (echogram) on the PC monitor (similar to a hard-copy record), annotation of the record, and storage of the raw data as binary files for use by post-processing software. Each frequency had a separate display/record. An example of an echogram is shown in Figure 4.

Figure 4. Example of echogram produced by Knudsen software. This echogram was collected in southern Sinepuxent Bay (Run 90; UTM N4235600, west to east). Record outputs for both frequencies are shown in a stacked display. The high frequency (200 kHz) record is on top, showing the position of the bay bottom. The bottom record represents the low frequency (28 kHz) output. A paleochannel is seen in the low frequency record.

Water level measurements

The soundings (depth data) collected by the echosounder are measurements of the 10 distance between the transducer and the top of the water-sediment interface (or whichever interface recognized). The level of the water surface (and the level of the whaler) fluctuated depending on the tide stage and degree of wind setup, both factors of which will vary depending on exact location in the coastal bays. To determine the actual water level during the time the hydrographic surveys were conducted, water level recorders were installed and operated at several locations within the areas being surveying. Information regarding the locations of the water level recorders shown in Figure 5 and times water level recorders were in operation at each location are presented in Table 3.

Additional water level observations were obtained from the tide gauges at the U.S. Coast Guard station in Ocean City, and in Sinepuxent Bay, and from a water level recorder in Ocean Pines Yacht Basin (See Table 3). The tide gauge at the Coast Guard Station, installed and maintained by the Army Corps of Engineers (COE), is included in the NOAA tide gauge network (Sta. No. 857-0283). The National Park Service maintains the tide gauge in Sinepuxent Bay. The Army Corps of Engineers installed the water level recorder in Ocean Pines Yacht Basin in conjunction with their hydrographic surveys in Isle of Wight Bay.

Water level recorder systems manufactured by Global Water Instrumentation, Inc. were used for this study. The system consists of a Global Logger III (GL300) data recorder interfaced with Global Water Level sensor (WL300). The level sensor is a submersible pressure transducer consisting of a solid-state pressure sensor encapsulated in a stainless steel submersible 3/4'” diameter housing. The sensor is connected to the data logger by a molded-on waterproof cable that is vented to the atmosphere. The vent to the atmosphere minimized offsets caused by barometric changes.

To minimize noise from wave activity, the sensor was mounted in a “stilling well” which consisted of a 5-foot length of 4 inch PVC pipe. The sensor was affixed to the inside wall of the pipe. The level of the sensor and a second level corresponding to 48 inches (1.22 m) above the sensor were marked on the outside of the pipe. The top and bottom of the PVC pipe were capped. To allow slow passage of water between the inside and outside of the pipe, four 1/8” holes were drilled through the PVC wall near the bottom of the pipe. The PVC pipe was securely mounted on a piling, with the bottom of the pipe positioned on or near the bay bottom.

The manufacturer calibrated the water level recorders prior to shipping. Calibrations were confirmed in the field prior to deployment and again at the end of the study

The data loggers were programmed and water level data were retrieved using a laptop computer and software supplied by the manufacturer. The data loggers were programmed to take a set of six readings every six minutes, recording the average of those readings. Time of day was synchronized with GPS time when water level data were transferred from loggers to the laptop and data loggers reset. Data output from the loggers included date, time of day, and water level in comma-delimited ASCII format. During the time hydrographic surveys were being conducted, the water level data were downloaded from the loggers every 4 to 7 days.

11 4260000 Locations of Water Level Recorders and Tide Stations 4258000 1 Delaware 4256000 Maryland

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Figure 5. Location of water level recorders and tide gauges used in this study. Information regarding recorders and gauges, identified by number, are listed in Table 3.

12 Table 3. Information on water level recorders and tide stations used in this study. Station numbers and locations are shown in Figure 5. Elevations for water level sensors were derived by GPS. Water Lever Date installed UTM Elevation of Date Water Level Sensor Location-description/ Sta # Sta ID Recorder (Date put on- NAD83-meters removed NAVD88-meters Comments Serial # line) Northing Easting (feet) Private bulkhead at Keenwick Road off Roy -1.03±0.02 1 Keenwick 5577 6/29/00 8/9/00 4256765 492454 Creek, in Delaware; although up for 30 day, only (-3.38±0.06) recorded last two wks: 7/26 to 8/9/00 -0.93±0.01 Ocean City Recreation Pier at 125th Street in 2 OC Rec Pier 5150 4/27/00 5/25/00 4253815 494499 (-3.04±0.05) Ocean City Isle of -0.48±0.001 Isle of Wight at Rt. 90 Bridge 3 5577 4/26/00 5/25/00 4248995 491156 Wight (-1.575±0.03) St. Martin -0.78±0.05 Hudson Family Marina at Holiday Harbor, 4 5576 4/26/00 5/24/00 4251847 484731 River (-2.56±0.15) upstream St. Martin River Private bulkhead on Bay Shore Dr. at 27th Street, 27th St -0.73±0.03 5 5577 8/9/00 10/5/00 4245557 492576 Ocean City; only recorded two weeks of data, (-2.40±0.10) from 9/13/00 to 10/5/00. Marsh -0.44±0.02 Marsh Harbor, on community pier 6 5576 5/26/00 6/8/00 4241781 490857 Harbor (-1.44±0.08) Snug -0.48±0.06 Snug Harbor, on private dock 7 5150 5/25/00 6/28/00 4238318 488648 Harbor (-1.57±0.20) Community dock at Rum Pt.; Programmed to -0.92±0.03 8 Rum Pt. 5576 8/10/00 9/13/00 4232155 485673 record water levels in Meters, TP6 disabled. Only (-3.03±0.09) recorded two weeks of data, 8/27 to 9/13/00 -0.54 ±0.03 South Pt. Boat Ramp 9 South Pt. 5577 5/25/00 6/28/00 4229841 483267 (-1.77±0.1) -0.82±0.02 Private dock in Newport Bay 10 NPB 5576 6/8/00 6/27/00 4231607 482812 (-2.68±0.08) Ocean Pines Army Corps Water level recorder in Ocean Pines 11 8/9/00 4248659 488803 -- Marina Yacht Basin NOAA tide station at US Coast Guard Station, 12 NOAA 8570283 Permanent 4242265 492034 -- Isle of Wight Bay National Park Service Tide Sta- Sinepuxent Bay 13 NPS-1 Permanent 4235328 488677 --

13 Elevation determinations of water level recorders

Given that the bathymetric data collected for this study is to be used primarily for scientific application rather than navigation, the North American Vertical Datum of 1988 (NAVD88) was used as the common vertical reference instead of Mean Lower Low (MLLW) datum that is traditionally used for navigation charts. NAVD88 is a fixed plane of reference for elevations on the North American continent and is independent of tidal datums, which vary significantly within a geographical area. Surface models developed from sounding data referenced to NAVD88 provide a true depiction of the bay bottom surface, whereas, surfaces derived from data adjusted to MLLW are “warped”. Also, at the onset of the study, local tide datums were not available for some portions of the study area. Using NAVD88 eliminated the need to determine those tide datums.

To adjust the water level data to NAVD88, each water level recorder site was surveyed to determine elevation of the water level sensor relative to NAVD88. One or more temporary benchmarks (BM) were set at each recorder site and relative elevations between the BMs and 4 ft reference marks on the stilling well of the recorders were determined by differential leveling. Elevations (NAVD88) of the BMs were later determined by GPS and/or by differential leveling from established NOAA benchmarks. Elevations determined by each method were within 6 cm of each other. Table 4 lists calculated water level for each of the recorders and comparisons of levels determined by the two methods.

Table 4. Comparison of tide station mean water levels (MWL) elevations in NAVD88 determined by GPS and traditional differential leveling. MWL was calculated by averaging recorded water level data at each site. Values are in meters, (feet in parentheses).

Water level MWL (GPS MWL (Trad. Water level MWL (GPS MWL (Trad. Station derived NAVD88) Station derived NAVD88) NAVD88) NAVD88)

Keenwick + 0.06 (0.21) - Marsh +0.06 (0.21) +0.006 (0.02) Harbor

OC Rec.Pier +0.07 (0.24) +0.13 (0.43) Snug Harbor +0.003 (0.01) -

Isle of Wight +0.02 (0.06) Rum Pt. +0.04 (0.15) -

Hudson -0.03 (0.11) - South Pt. -0.04(0.13) -0.03 (0.10) Marina

27th Street, +0.12 (0.41) +0.05 (0.17) Newport Bay -0.01 (0.04) +0.05 (0.18) OC

Several problems were encountered with the differential leveling surveys. Although listed as recently recovered in the NOAA database, several National Geodetic Survey (NGS) BMs could not be found or had been disturbed or destroyed. As a result, some of the water level

14 recorder sites could not be surveyed using the differential leveling method. Final elevations for all recorders were determined by GPS. Details and quality assurance-quality control (QA/QC) for the GPS and differential leveling techniques are presented in Appendix A. Elevations (NAVD88) of the water level recorder (water level sensors) are listed in Table 3.

Water level data reduction and tide analyses

Water level data from all recorders were imported into a spreadsheet and synchronized to common time intervals (exactly six minutes or 0.1 hour intervals) using a MathCAD splining technique (MathSoft, Inc., 1998). Water levels from each recorder were then plotted against time and preliminary tidal datums were calculated. The water level data from the NOAA tide gauge located at the Coast Guard Station were used as a reference for all other tide data collected for this project. The NOAA tide gauge is located near the Ocean City Inlet, thereby reflecting the maximum of the tidal range for the northern coastal bays. The tide gauge was in operation for the entire time of this project, providing a continuous tide data set inclusive of the times during which MGS water level recorders were in operation.

Hydrographic Survey Data Processing

Depth data filtering The sounding data from the hydrographic surveys were processed to remove noise and invalid depth readings. The ASCII comma-delimited text files (kea files) outputted by the Knudsen echosounder were imported into spreadsheets. Each day’s worth of sounding data were combined into a single spreadsheet. A series of sorting routines were used to filter out invalid HF depth data (invalid HF flag), depths less than 0.32 meters (detection limit of the Knudsen), “out of sequence” depths (e.g., fish, water column noise, multiples, etc.), and invalid location coordinates (GPS latency values > 2000 msec).

Sounding depth adjustments Sounding depth values were adjusted to account for the offset of the transducer below the water surface. The offset value was derived from the calibration of the echosounder (See Appendix A). The following equation was used:

Depth adj= 1.01377 * depth measured + 0.1878

Where: the value 0.1878 is the transducer offset in meters, and 1.01377 is a correction factor for the speed of sound Both depth adj and depth measured are in meters.

The adjusted sounding depth values were then corrected to account for tide stage and/or wind effects. For the St. Martin River, Assawoman Bay and Newport Bay, this correction was 15 fairly straightforward. Comparisons of synchronized water level data from the recorders operated in the St. Martin River, on Isle of Wight and at the Ocean City Recreation Pier, indicated little difference in tide range and timing of tide stage, so data from a single recorder were used to correct the soundings for each sub-basin. St. Martin River soundings were corrected using data from the Isle of Wight recorder; Assawoman Bay soundings were corrected using the Ocean Rec. Pier data. Comparisons of synchronized water level data from the recorders at South Pt. and Newport Bay also indicated little difference in tide range and time, so Newport Bay soundings were corrected using data from the recorder in Newport Bay. Using a MathCAD splining routine (See Appendix D), water levels from the specific recorder were interpolated to the exact times depth sounding were taken, and the interpolated water level were subtracted from the adjusted depth soundings, obtaining depths corrected to NAVD88.

Tide analyses for Sinepuxent Bay showed a significant decrease in tide range, and time delay in tide phase with distance from the inlet (Figure 6). To account for this significant attenuation in tide range, tidal corrections for soundings collected in Sinepuxent Bay were calculated using one of two methods. For depth soundings collected north of the Marsh Harbor and south of South Point, tidal corrections were interpreted using data from a single water level recorder (Marsh Harbor and South Pt., respectively) using the same method as described for the other sub-basins.. For depth soundings collected between tide stations (i.e., Marsh Harbor and Snug Harbor; or Snug Harbor and South Pt.), tidal corrections were calculated using a two-step process. 1.) Water levels from each recorder were interpolated for exact times soundings were collected. 2.) From the time-interpolated water levels, a water level for each sounding location was interpolated using a weighted factor based on the distance the sounding location was between two adjacent water level recorders (See Appendix D for MathCAD routine). The method assumes that the attenuation of the tides is linear between stations.

Sinepuxent Bay Tides

1.00 Mean Tide Range 6 (meters) 0.80 Time lag (hours) from 5 Inlet 4 0.60 3 Hours

Meters 0.40 2

0.20 1

0.00 0 0 2000 4000 6000 8000 10000 12000 14000 Distance (meters) from Inlet

Figure 6. The graph illustrates the change in tide range and tidal phase progression (time lag) in Sinepuxent Bay with distance from Ocean City Inlet (Marsh Harbor). The southern most data point on the graph is South Pt. 16

Gridding techniques for bathymetry model

Final adjusted bathymetric data were interpreted with Surfer â 7 software package. In Surfer, the adjusted data was processed using Triangulations with Linear Interpolation (TLI) method (Golden Software, Inc., 1999). Using a vector shoreline digitized from rectified 1989 and 1999 aerial photography to define the land-water interface (0 depths), a 10 meter regularly spaced grid was calculated from the bathymetric data. The TLI method is an exact interpolator and honors every data point, creating a surface that best represents the original data and shoreline. The regularly spaced grids were used to create the bathymetry maps (Plates 1-3).

Data accuracy

The Ashtech GPS-Starlink DGPS system provides for ± 1.5-meter accuracy. The accuracy of the post-processed horizontal GPS data is ±3.5 meters. The figure takes in account of the average boat speed (4 knots or 2 m/sec) and GPS coordinate update latency (1000 msec). The accuracy of the post-processed bathymetry data is estimated to be ± 0.2 meters (0.7 ft). This estimate takes in account of the error introduced with the water level adjustments and elevation accuracy of the water level recorders.

Discussion

Bathymetric Grid

The bathymetry maps were produced not from the original soundings, but from a gridded data set that consist of data points interpolated from the original data and the shoreline. Any feature missed by the original data (i.e., features less than 200 meters in size and lying between hydrographic survey lines, or features outside of surveyed areas) would not show up on the grid. Also, some triangular contour patterns seen in the maps are an artifact of the gridding technique. An example of this may be seen in the middle of Newport Bay (Plate 3). The linear feature defined by -1.5- meter contour follows a hydrographic survey track line. The adjusted depths along this line were close to -1.5 meters.

Overview of the Bathymetry of the Northern Coastal Bays

Bathymetry maps show that most areas surveyed are shallow, less than 2.0 meters (6.5 ft) deep. The mean depth is 1.5 meters. Most of the deeper areas (greater than 3 meters) are a result of dredging associated with developed shorelines. The two deep holes (maximum depth 6.18 meters) seen along the south side of St. Martin River were dredged for fill during the 17 construction of the Ocean Pines community (Plate 1). The same holds true for the deep holes seen along the eastern shore of Assawoman Bay. These artificially deep areas, with depths up to 9.8 meters, are a result of dredging for fill during the construction of the various Ocean City communities, or for beach fill to restore Ocean City beaches after the 1962 storm (USACE, 1980;Wells and others, 1994).

In Sinepuxent Bay, the Federal Channel that runs axially along the bay is the most dominate feature (Plate 2). Most of the areas deeper than 3 meters fall within the channel. Also, the channel segment between the Inlet and Snug Harbor takes on a natural sinuous course, most likely as a result of the westward migration of Assateague Island by overwash processes and the higher water currents from the Inlet. The channel segment to the south maintained its artificially straight course as originally dredged by the Army Corps of Engineers in 1930s.

Newport Bay bottom is rather featureless, with almost all areas having depths less than 2 meters (Plate 3). The only deep area is at the mouth of the Trappe Creek (top of the bay) where depths reach 4 meters. This area is thought to be naturally deep, scoured by a current flowing in and out of Trappe Creek.

Tides

Based on the water level data collected in the study, some general observations may be made regarding the tide patterns in the northern coastal bays. Preliminary tidal datums for the water level stations are presented in Tables 5 and 6. Although these datums are based on observations for time intervals of less than 30 days (i.e., not a full lunar cycle), the datums are somewhat similar to published and unpublished datums from NOAA (James Hubbard, pers. comm. 4/10/00). Deviations from published datums are attributed to effects of wind setup skewing short-term data. An example of weather effect on tide may be seen in data from South Pt (Figure 7). Between May 29 and May 31, 2000, South Pt. water levels dropped as a result of steady winds pushing the water away for the tide gauge. Water levels recorded at other sites in Sinepuxent Bay for the same period followed more normal trends.

In the northern coastal Bays, the maximum tide range is approximately 0.6 meters (2 ft.) at Ocean City Inlet and diminishes with distance from the Inlet. North of the Inlet, most of the tide attenuation occurs around 27th Street (Bayshore Estates), at which point Isle of Wight widens dramatically. North of the Rt. 90 bridges, the mean tide range is relatively constant at 0.3 meters (1 ft). The tide phase progression (lag time) at the Rt. 90 Bridges averages 2.5 hours after the NOAA tide station and 3.2 hours at Keenwick Estates in northern Assawoman Bay (Delaware).

South of the Inlet, the mean tide range drops from 0.7 meter at Marsh Harbor, which is located at the Inlet, to 0.1 meter at South Pt. Boat Ramp (Figure 6). The average tide phase lag time observed at South Pt. is 4.8 hours behind Marsh Harbor.

18 Water Levels in Sinepuxent Bay

2.50

2.00

1.50

1.00

0.50

0.00

-0.50 1-Jun 2-Jun 3-Jun 4-Jun 5-Jun 6-Jun 7-Jun 8-Jun 9-Jun 26-May 27-May 28-May 29-May 30-May 31-May Height (feet, NAVD88) -1.00

-1.50 Marsh Harbor NOAA-USCG -2.00 Snug Harbor South Point -2.50 Day

Figure 7. Plot of time-synchronized water levels for Sinepuxent Bay.

Table 5. Comparison of preliminary tide datums for water level recorders operated in Assawoman and Isle of Wight Bay. Elevations are in meters NAVD88. Ocean City, NOAA Hudson Isle of Fishing Pier (Coast OC Pier Keenwick Marina Wight (Atlantic) Guard Sta) (St. Martin R.) Time interval 1982-1989 7/23-8/7/00 5/8-5/19/00 5/8-5/19/00 5/8-5/19/00 5/8-5/19/00 Mn* 1.04 0.62 0.31 0.30 0.29 0.30 MTL -0.20 0.03 0.24 0.25 -0.11 DHQ 0.12 0.12 0.05 0.06 0.11 0.08 DLQ 0.05 0.08 0.02 0.05 0.07 0.02 Gt 1.21 0.81 0.37 0.40 0.47 0.41 DTL -0.15 0.06 0.25 0.28 -0.05 Time lag from Coast Guard -0.1 0 2.5 2.8 3.2 2.7 Station (hrs)

Table 6. Comparison of preliminary tide datums for water level recorders operated in Sinepuxent Bay. Elevations are in meters NAVD88. NOAA Sta Marsh Snug Rum Pt. South Pt. (Coast Guard Sta) Harbor Harbor Time interval 5/26-6/8 8/27-9/9 5/26-6/8 5/26-6/8 8/27-9/9 5/26-6/8 Mn* 0.69 0.58 0.72 0.33 0.20 0.11 MTL -0.13 0.00 0.05 0.06 0.00 0.11 DHQ 0.11 0.09 0.16 0.07 0.00 0.02 DLQ 0.06 0.12 0.00 0.08 0.00 0.04 Gt 0.86 0.80 0.88 0.48 0.26 0.17 DTL -0.08 -0.03 0.21 0.05 0.00 0.09 Time lag from 0.00 0.83 3.05 4.77 Coast Guard Station (hrs) * Mean Range (Mn) = MHW-MLW Mean Tide Level (MTL) = Avg(MHW + MLW) Diurnal High Water Inequality (DHQ)= MHHW - MHW Diurnal Low Water Inequality (DLQ)= MLW- MLLW Gross Mean Range (Gt) = MHHW - MLLW Diurnal Tide Level (DTL) = Avg(MHHW + MLLW)

20 Applications of bathymetry and tide data

The XYZ sounding data from this project is currently being incorporated into a circulation model developed by the Waterway Experiment Station of the U.S. Army Corps of Engineers in Vicksburg, Mississippi. The water level data will be used to help calibrate the model. The Hydrodynamic and Geomorphic Model was developed for the Baltimore District for their rehabilitation of the south jetty to the Inlet. However, the model has been expanded to include areas extending into the coastal bays and will be very useful in understanding circulation patterns and sediment/nutrient transport in the coastal bays. Details on a similar model for Shinnecock Bay and vicinity in New York may be found at the following web site: http://cirp.wes.army.mil/cirp/studies.html

Recommendations for future work

The bathymetric data presented in this study does not include Isle of Wight Bay, which was surveyed by the Baltimore District of the Army Corps of Engineers. The addition of the Corps’ hydrographic data to the XYZ data set would require re-adjustment of the soundings to NAVD88. However, incorporation of the data into the gridded data set used to produce the bathymetry maps may require additional surveys in the Isle of Wight Bay to fill in data gaps and perimeter surveys.

Systematic hydrographic surveys should be continued into Chincoteague Bay to provide continuous consistent coverage. Assuming that the bottom characteristics of Chincoteague Bay are similar to that of Newport Bay, a line spacing less than 200 meters may be adequate. However, in certain areas characterized by islands such as Johnson Bay area, a denser line spacing may be considered.

In this study, establishing vertical control at the tide stations proved to be very time consuming due to the lack of established vertical control bench marks in the study area, and the inadequate documentation for control points established by other groups. Future hydrographic work should include funding for high order GPS elevation surveys and for the establishment of additional GPS reference stations to be used with the existing High Accuracy Reference Network (HARN). These reference stations can be used to set up reference baseline when conducting GPS surveys to determine elevations of water level recorders and tide gauge sensors. The establishment of additional GPS reference stations will be necessary in the southern coastal bays area where established vertical control network of benchmarks is sparse or non-existent. GPS surveys will have to be used with differential leveling to establish vertical in the southern bays area.

Acknowledgements

This study would have been difficult, if not impossible, to complete without the assistance and support of a long list of individuals and groups. The authors extend their gratitude

21 to all who were involved in many ways. Mr. P.J. Aldridge and the Marsh Harbor Community, Mr. and Mrs. Richard Ewing, Dr. F. Robert Haase, Mr. George J. Hess, Mr. and Mrs. James Hudson, Mr. Tom Patton, Thomas Shuster with Ocean City Recreation an Parks, and Mr. and Mrs Tomlinson graciously allowed us to install the water level recorders on their property. Ms. Carol Ann Hall of O’Connor, Piper and Flynn and Ms. Katherine Winkler handled arrangement for the rental house, which served as home for MGS staff during twelve weeks of fieldwork. Mr. David Ferguson and the Ocean Pines Association provided logistical support during field operations. Mr. Thomas F. Johnson, Jr. provided support for the recovery and use of a NGS benchmark located on his property. Tom Waddington of the Baltimore District of the U.S. Army Corps of Engineers, assisted in coordinating hydrographic survey efforts of the Army Corps’ with MGS, and provided Army Corps staff and equipment to conduct GPS surveys. Mr. Harold Catlett and Mr. Tony Sazaklis of the Baltimore District of the U.S. Army Corps of Engineers, conducted the surveys for the GPS determination of elevations at the water level recorders. Mr. Tom Chessar and crew from Engineering and Construction Service, Maryland Department of Natural Resource, conducted differential leveling surveys to determine elevations of the water level recorders. Fellow MGS staffers Robert Conkwright, Tim Bethke, Lamere Hennessee, Jeffrey Halka, William Panageotou, and Geoffry Wikel assisted in conducting hydrographic surveys. Jeanne Gary and Dorothy Holmes, also of MGS, provided logistical support for the project.

The Fisheries Service of the Maryland Department of Natural Resources provided funding for this study.

22 References Cited

Casey, J. and Wesche, A., 1981, Marine Benthic Survey of Maryland’s Coastal Bays, Report submitted by the Maryland Dept. of Natural Resources, part one, p. 1-21.

Dean, R.G., Perlin, M., and Daly, B., 1978, A coastal engineering study of shoaling in Ocean City Inlet, Report by Dept. of Civil Engineering, Univ. of Delaware for Baltimore District, U.S. Army Corps of Engineers, March 1978, 135 pp.

Golden Software, Inc., 1999, Surfer â 7 User’s Guide, Golden, Co, 619 pp.

International Hydrographic Organization, 1998, IHO Standards for Hydrographic Surveys, 4th Edition, April, 1998, Special Publication No. 44, International Hydrographic Bureau, Monaco, 23 pp.

Knudsen Engineering Limited, 1999, 320 Series Echosounder: Online Scsi Control Software Manual, Supports Software: ECHO CONTROL.EXE V2.00, Revision 3.0, Nov 5, 1999, Knudsen Engineering Limited, Perth, Ontario, Canada.

Leatherman, S.P., 1979, Migration of Assateague Island, Maryland, by inlet and overwash processes, Geology, vol. 7, p. 104-107.

Maryland Coastal Bays Program, 1999, Today=s Treasures for Tomorrow: Towards a Brighter Future- A Comprehensive Conservation and Management Plan for Maryland=s Coastal Bays, Final Draft, June, 1999 Berlin, Maryland, 181 pp.

MathSoft, Inc., 1998, MathCAD 8: User’s Guide, Cambridge, Massachusetts, 372 pp.

NOAA, (no date) NOS Hydrographic Surveys: Specifications and Deliverables (Draft), U.S. Dept. of Commerce, National Oceanic and Atmospheric Adm., National Ocean Survey.

U.S. Army Corps of Engineers (USACE), 1980, Atlantic coast of Maryland and Assateague Island, Virginia: Main Report, feasibility report and final environmental impact statement, Baltimore District.

U.S. Army Corps of Engineers (USACE), 1998, Ocean City, MD and Vicinity Water Resources Study: final Feasibility Report and Environmental Impact Statement with Appendices, Baltimore District, Baltimore, MD, June, 1998, released on CD-ROM.

Wells, D.V, Conkwright, R.C., Hill, J.M., and Park, M.J., 1994, The surficial sediments of Assawoman Bay and Isle of Wight Bay in Maryland: physical and chemical characteristics, Coastal and Estuarine Geology Program File Report No. 94-2, Maryland Geological Survey, Baltimore, MD, 99 pp.

23 Wells, D.V., Conkwright, R.D., Gast, R., Hill, J.M., and Park, M.J., 1996, The shallow sediment of Newport Bay and Sinepuxent Bay in Maryland: physical and chemical characteristics, Coastal and Estuarine Geology Program File Report No. 96-2, Maryland Geological Survey, Baltimore, MD, 116 pp.

Appendix A- Quality Assurance/Quality Control

1. Echosounder depth calibration

The Knudsen echosounder was checked against known depths to reduce errors. On June 27, 2000, the echosounder was calibrated throughout the entire range of water depths measured. The data collected and the regression of the calibration data is located in the presented in Table. All initial depth recordings were made assuming a speed of sound of 1500 meters per second. The recorded depths were adjusted after collection using a calibration equation derived from the calibrations conducted in the field.

Table 7. Regression analysis of calibration data for Knudsen echosounder. Measured Measured Direction Observed Depth Depth Depth Echosounder Feet Meters reading (HF) Down 3 0.91 0.74 Down 4 1.22 1.02 Down 5 1.52 1.32 Down 6 1.83 1.62 Down 7 2.13 1.88 Down 8 2.44 2.18 Down 9 2.74 2.48 Down 10 3.05 2.8 Down 12 3.66 3.43 14 4.27 4.08 Up 12 3.66 3.41 Up 10 3.05 2.82 Up 9 2.74 2.53 Up 8 2.44 2.24 Up 7 2.13 1.92 Up 6 1.83 1.63 Up 5 1.52 1.32 Up 4 1.22 1.00 Up 3 0.91 0.72 Up 2 0.61 0.45

A 1

Table 7. Regression analysis of calibration data for Knudsen echosounder (Cont.) SUMMARY OUTPUT

Regression Statistics Multiple R 0.999705265 R Square 0.999410616 Adjusted R Square 0.999377872 Standard Error 0.025346899 Observations 20

ANOVA df SS MS F Significance F Regression 1 19.60955642 19.60955642 30522.36032 1.59212E-30 Residual 18 0.011564375 0.000642465 Total 19 19.62112079

Standard Coefficients Error t Stat P-value Lower 95% Upper 95% Intercept 0.1878 0.012808654 14.6622686 1.88574E-11 0.160893916 0.214713923 X Variable 1 1.01377 0.005802699 174.7064976 1.59212E-30 1.001578112 1.025960165

A 2

2. Elevation determinations of water level sensors

The following tables contain leveling data for the water level recorders installed by MGS for this study. Superscript numbers refer to notes on surveying details; notes are presented at the end of the tables. All elevations are orthometric elevations, NAVD88, in feet (meters, if indicated, in parentheses).

Table 8. Elevation leveling data for the water level recorder installed on a private bulkhead in Keenwick Community, in Delaware.

Point ID Point Description. MGS Stadia GPS derived GPS derived location 3 Comments level (ft) 15 elevation 3

A Nail bulkhead above 4.27 3.27 "0.06 Leveling survey piling with stilling well and 2nd GPS survey were not done

B (KW01) Harold=s PK nail, on 4.48 3.06 "0.06 38 27 32.43115 Keen Wick Road (0.934 "0.02) 75 5 12.872

C (KW02) Rich=s PK nail, on very 4.42 3.12 "0.06 end of Keen Wick Road

D South rim of Manhole 4.62 2.92 "0.06 cover on Keen Wick Road

4 ft nail on piling 6.93 0.61"0.06

Water level sensor -3.38 "0.06 Calculated elevation

Average water level based on data from 7/26 to 8/9 = 3.59 ft station datum A 3

Table 9. Elevation leveling data for the water level recorder installed on the Ocean City Recreation Pier (125th Street, Ocean City).

Point Point MGS GPS GPS GPS GPS Elevation Comments Elevation ID Description. Stadia derived derived derived derived based on difference - level elevation location 3 elevation location 6 leveling GPS -Level (ft) 5 3 6 survey 8

A B GPS3 GPS6

A Nail in center 5.13 3.16600 38 25 3.31 37 25 3.51 3.37 -0.34 -0.20 (125S) of Pier next to 55.76686 "0.05 55.77141 +0.02 AA@ piling holding 75 03 (1.008 75 03 elev. WLR 45.77401 "0.015 45.77061 m)

B 4 ft nail on 7.48 0.95 1.15 +0.02 piling "0.05

C PK set DNR 4.85 +0.01 AC@

Water level -3.04 -2.85 +0.02 Calculated sensor "0.05 elevation, based on level AA@

Average water level based on data from 5/2 to 5/25 = 3.28 ft station datum

A 4

Table 10. Elevation leveling data for the water level recorder installed on the steel bulkhead at the southeast point of Isle of Wight.

Point Point MGS GPS GPS derived GPS GPS derived Elevation Comments Elevation ID Description. Stadia derived location 3 derived location 6 based on difference level elevation 3 elevation 6 leveling - GPS - (ft) 5 survey 7 Level

A Rebar on cement run, 4.405 5.40681 38 23 5.56 -0.15 6th rebar from water edge, row closest to 21.39679 "0.03 WL recorder, rebar 75 06 marked with COE Î 04.92374

B nail on top of piling 2.455 7.357 7.51 Calculated holding WL sensor elevation

C 4 ft nail 7.54 2.272 2.425 Calculated elevation

D Greg 2000 2.687 ft 38 23 19.80569 2.68* 75 06 30.84883 BM (0.819 m)

Rebar (Gary) 2.82 w/cap BM-

Water level -1.728 -1.575 Calculated sensor "0.03 elevation

Average water level based on data from 4/26 to 5/25 = 1.64 ft station datum * Elevation used is GPS elevation obtained from Baltimore District, U.S. Army Corps of Engineers (ACOE) (Harold Catlett, pers. communication-email).

A 5

Table 11. Elevation leveling data for the water level recorder installed on a piling at the Hudson Boat Marina (Holiday Harbor) in St. Martin River.

Point ID Point Description. MGS GPS derived GPS derived location 3 Calculated elevations Comments Stadia elevation 3 from GPS derived level (ft) 5 elevations

A Nail on wooden 4.84 2.80839 38 24 54.30985 No leveling bulkhead at land 75 10 30.21211 survey was end of small dock done

B 4 ft nail on piling 6.21 1.44 +0.15?

Water level sensor -2.56 +0.15?

Average water level based on data from 4/27 to 5/24 = 2.45 ft station datum

A 6

Table 12. Elevation leveling data for the water level recorder installed on a private bulkhead in Bayshore Estates in Ocean City (~27th Street).

Point Point Description. MGS Stadia GPS GPS Elevation based Comments Elevation ID level (ft) 9 derived derived on leveling difference elevation 6 location 6 survey 10 GPS vs. Level

H Nail in parking lot on east 3.62 4.395 5.69 "0.10 38 21 5.49 "0.01 +0.20 (27TH) side of Bayshore Dr., also (1.73 "0.03 29.54327 called PK C by T. Chesser m) 75 05 3.87548

R 2nd nail in parking lot on 4.49 5.60 "0.10 5.39 east side of Bayshore Dr. "0.01

A Nail on to pier above 6.00 3.31 "0.10 3.07 stilling well (PK A) "0.01

B SE corner of deck area 4.55 "0.01

4ft nail on piling 1.60 "0.10 1.36 Calculated elevation; "0.01 4 ft nail on piling is 1.708 ft (20.5") below PKA

Water level sensor -2.40 "0.10 -2.638 Calculated "0.01 elevation

Average water level based on data from 9/15 to 10/2 = 2.81 ft station datum

A 7

Table 13. Elevation leveling data for the water level recorder installed on the community pier in Marsh Harbor Marina.

Point ID Point MGS GPS GPS derived location 6 Elevation Comments Elevation Description. Stadia derived based on difference level (ft) elevation 6 leveling GPS vs 11 survey 12 Level.

MH01 Manhole cover- 4.695 8.64 "0.08 38 19 26.32401 8.42 Manhole is +0.22 south rim (2.63 "0.02 75 06 13.27522 "0.01 north 279 ft m) from nails in dock

A Nail south of 4.45 8.67 manhole (Rich=s "0.01 Pt.)

B 3 nails in dock, 9.50 3.83 "0.08 3.64 directly above 4 "0.01 ft nail in piling

4 ft nail in 2.56 "0.08 2.37 4 ft nail is 1.27 piling "0.01 ft (15.25") below three nail in top of Marsh Harbor community dock.

Water level -1.44 "0.08 -1.63 Calculated sensor "0.01 elevation

Average water level based on data from 5/26 to 6/8 = 1.65 ft station datum

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Table 14. Elevation leveling data for the water level recorder installed on a private bulkhead in Snug Harbor.

Point ID Point Description. MGS Stadia GPS derived GPS derived location 3 Comments level (ft) 13 elevation 3

A Nail on dock 7.01 1.73 " Leveling survey and 2nd GPS survey were not done

B (SNUG) Nail on Snug Harbor 5.98 2.75 "0.20 38 17 35.99749 Road (0.837 "0.06 m) 75 07 48.11415

C 4 ft nail on piling 6.30 2.43 "0.20

Water level sensor -1.57 "0.20 Calculated elevation

Average water level based on data from 5/25 to 6/28 = 1.58 ft station datum

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Table 15. Elevation leveling data for the water level recorder installed the Rum Point community dock in Sinepuxent Bay.

Point ID Point Description. MGS Stadia GPS derived GPS derived location 3 Comments level (ft) 14 elevation 3

A (RP01) Nail at land end of dock 3.84 3.44 "0.09 38 14 14.16142 Leveling survey (1.05 "0.03 m) 75 9 49.48292 and 2nd GPS survey were not done

B (RP02) NE corner of bulkhead 4.90

C Nail on top of dock 4.02 3.26 "0.09 directly over piling with stilling well

4 ft nail on piling 0.97 "0.09 4 ft nail is 2.29 ft (27.5” below pt. C

Water level sensor -3.03 "0.09 Calculated elevation

Average water level based on data from 8/27 to 9/13 = 3.18 ft station datum

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Table 16. Elevation leveling data for the water level recorder installed on a bulkhead at the South Point boat ramp.

Point Point MGS GPS GPS derived GPS GPS derived Elevatio Commen Elevation ID Description. Stadia derived location 2 derived location 3 n based ts difference - level elevation elevation on GPS -Level 1 2 3 (ft) leveling 2 3 survey4 GPS GPS

A NOS BM 5.51 1.85367 38 12 1.67 "0.1 38 12 1.65 0.20 0.02 (0536 0536 A 58.84180 (0.508 m 58.84290 "0.05 ) 75 11 "0.03) 75 11 29.55556 29.55704

B NOS BM 3.96 3.22 3.26 0536 B "0.03 "0.05

C PK C nail- 9 5.00 2.18 2.16 ft from "0.03 "0.05 piling

D 4 ft nail on 4.95 2.23 2.21 Calculate piling "0.03 "0.05 d elevation

Water level -1.77 -1.79 Calculate sensor "0.03 "0.05 d elevation

Mean Water Level for station, based on reading from 5/26 to 6/15 = 1.64 ft. (sta. datum)

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Table 17. Elevation leveling data for the water level recorder installed on a private dock Newport Bay.

Point ID Point MGS Stadia GPS derived GPS derived Elevation based Comments Elevation Description. level (ft) 1 elevation 3 location 3 on leveling difference survey 4 - GPS - Level

GPS3

A nail on CL of 5.48 (DH02) dock, landward

B nail on mid pier of dock, 6.40 2.82 "0.08 38 13 56.38442 2.95 -0.13 10.9 ft from NE edge (DH01) (piling) and 6.6 ft from (0.861 "0.024 75 11 47.16933 "0.02 West edge.

C 4 ft nail on 7.90 1.32 "0.08 1.46 piling "0.02

D Water level -2.68 "0.08 -2.54 Calculated sensor "0.02 elevation

Mean water level based on data from 6/9 to 6/15 = 2.72 ft. station datum

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Notes on vertical control surveys and data presented in Tables 8 through 17:

1 Stadia rod readings were taken by Darlene V. Wells (DVW) on 6/27/00 using level (Universal LT 8-300 David White Transit) borrowed from National Park Service (Carl Zimmerman, National Seashore, Resource Manager). Readings are not reference to any datum, just the height read from the stadia rod.

2. GPS data for GPS derived elevations were collected on 5/5/00 by Harold Catlett and Tony Sazaklis, both with Baltimore District of U.S. Army Corps of Engineers, using an Ashtech .Z12 Dual Frequency Receiver, Ashtech Office Suite for Survey (AOS Ver. 2.00) Software to process GPS data; Tripod height = 207.2 cm (6.7979 ft). Base stations were set up at NGS HARN BM at North Beach (North_Beach_2) on Assateague Island, and at BM02 located at the Ocean Pines Marina. (Specifications and QA/QC for BM02 may be obtained from Baltimore District Army Corps of Engineers.) Elevation given is orthometric height calculated by subtracting geode height (GEODE96) from elliptical height determined by GPS. Survey results and QA/QC from AOS are presented in Tables 19 and 20 in Appendix I.

3 GPS data for GPS derived elevations were collected during week of 10/2/00 by Richard Ortt, Jr., and Harold Catlett. MGS tripod height = 204.0 cm (6.6929 ft). Base stations were set up at NGS BM at North Beach (North_Beach_2) on Assateague Island, and at Ocean Pines Marina on BM02. Survey results and QA/QC from AOS are presented in Tables 19 and 20 in Appendix I.

Table 18. National Geodetic Survey vertical control benchmarks used as check points during GPS surveys.

Date of NGS BM NGS GPS-derived GPS-derived Difference survey (vertical Published elevation location between control) ID elevation GPS and (PID) (NAVD88) Published

5/5/00 U 141 12.67 ft 12.99 ft +0.32 (HU1041)

10/2/00 L 56 3.57 ft 3.64 "0.07 ft 38 12 +0.07 (HU0397) 4986918 75 11 56.77407

4 Differential leveling surveys were conducted by Tom Chesser=s team (VM, KW, and JF) of Public Lands Division of the Md. Department of Natural Resources (DNR), on 10/3/00, transferring elevations from NGS BM L56 (Published NAV88 elevation 3.57 ft) which is located at the SE corner of Mr. Johnson=s house at South Pt. The team established a temporary benchmark (TBM-SP1, elevation of 2.97) at the centerline of South Pt. Rd at Waterside Dr, and closed back to L56 within -0.03 ft. Starting at TBM-SP1, team transferred elevations to three points at the boat ramp where MGS water level was located and closed back to TBM-SP1

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within-0.02 ft. The three points at the boat ramp NOS BMs 0536 B and 0536 A, and a PK nail (PK C) located 9 ft north of the piling on which the water level recorder was attached. The NOS BM are tidal bench marks installed in 1985 by NOAA as reference for tide station MD 857 0536 which was in operation for the period from 8/85 to 10/85. The benchmarks were never referenced to NAV88. For Dr. Haase=s dock, elevation was carried from TBM-SP to a second temporary BM (TBM-SP2, elevation 6.57 ft) at the center line of South Pt. Rd at Terrapin Pt. Rd, and closed back to TBM-SP1 within +0.03 ft. From TBM-SP2, elevation was transferred to Dr. Haase=s dock, to two points (PK nail on dock and 4 ft nail on piling), and closed back to TBM- SP2 within 0.00 ft.

5 Stadia rod readings were taken by DVW on 5/11/00 using level (Universal LT 8-300 David White Transit) borrowed from NPS (Carl Zimmerman). Readings are not reference to any datum, just the height read from the stadia rod.

6 Elevation and geographical coordinates for the BM were obtained from Harold Catlett, Baltimore District of the U.S. Army Corps of Engineers, Hydrographic Division.

7 Differential leveling surveys were conducted by Tom Chesser=s team (VM, KW, and JF) on 10/5/00, transferring elevations from ACOE BM (GREG) which is located at south end of St. Martins Neck Road, west side near the water. BM is a brass disc stamped AGREG 2000".

8 A: Differential leveling surveys were conducted by Tom Chesser=s team (VM, KW, and JF) on 10/4/00, transferring elevations from NGS BM OC 9 (PID HU1167) located at SE corner of OC Fire Sta. #4, at 130th Street, NAVD88 elevation= 2.750 m (9.02 ft). They established a temporary BM at the landward end of the Recreation Pier, PK nail in asphalt path, PK set DNR AC@, elevation = 4.85 ft, closed back to OC 9 within +0.01 ft. Then from DNR AC@, carried elevation to nail at centerline of pier (PK A) and 4 ft nail in piling (PK B), closing back to DNR AC@ within +0.01 ft. B: Differential leveling survey was conducted by George Young Surveyors on 5/31/00 for Ron Gatton of Environmental Consultants, Inc. Young Surveyors transferred an elevation from NGS BM OC 12 (PID HU1170) located at Jamestown Road and Coastal Hwy, NAVD88 elevation= 4.46 ft., to nail at centerline of pier (PK A), and closed back to NGS BM OC9 within 0.00 ft. Equipment used was a Topcon APL-1A.

9 Stadia rod readings were taken by Darlene Wells on 10/3/00 using a Leitz B1 Self-Leveling Transit. Readings are not reference to any elevation, just the height intercepts from the stadia rod. Level set up at two points. 1st point, took readings for H and A; 2nd point, took readings for H and R.

10 Differential leveling surveys were conducted by Tom Chesser=s team (VM, KW, and JF) on 10/4/00, transferring elevations from NGS BM OC1 (PID HU1159) located at the NW corner of the Amer. Legion Post at 24th Street on Coastal Highway, NAVD88 elevation = 5.99 ft. Chesser=s Team established a temporary BM at PK AC@ and closed back to OC 1 within +0.01 ft. PK AC@corresponds to point H located in the parking lot on the east side of Bayshore Drive, directly across from unit 29 (Mr. Hess apt.) whose dock we attached WLR. From PK AC@ (elevation 5.39 ft), elevations were transferred to points A and B, and closed back to PK AC@

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within 0.00 ft.

11 Stadia rod readings were taken by Darlene V. Wells on 10/3/00 using a Leitz B1 Self-Leveling Transit. Readings are not reference to any datum, just the height read from the stadia rod.

12 Differential leveling surveys were conducted by Tom Chesser=s team (VM, KW, and JF) on 10/5/00, transferring elevations from NGS BM G 104 (elevation = 13.86 ft) located on top of the south curb wall of the west end of Rt. 50 bridge crossing Isle of Wight bay to Ocean City. The team transferred elevation to top of a small headwall, elevation 4.73 ft. and closed back to G 104, within 0.00 ft. From the headwall, elevation was carried to manhole cover, and points A and B, and closed back to headwall within -0.01 ft.

13 Stadia rod readings were taken by DVW on 6/28/00 using level (Universal LT 8-300 David White Transit) borrowed from NPS (Carl Zimmerman). Readings are not reference to any datum, just the height read from the stadia rod.

14 Stadia rod readings were taken by DVW on 8/10/00 using a Leitz B1 Self-Leveling Transit. Readings are not reference to any datum, just the height read from the stadia rod.

15 Stadia rod readings were taken by DVW on 10/3/00 using a Leitz B1 Self-Leveling Transit. Readings are not reference to any datum, just the height read from the stadia rod.

Based on NOAA (NOS) tide data collected in 1984 for coastal bays, MTL is approx. 0.71 ft below NAV88.

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3. Post-Processing Data- GPS Surveys

Missing data: GPS post processing information for survey data collected May 5, 2000 by Harold Catlett and Tony Sazaklis; and specifications for USACE Reference benchmark BM02.

Table 19. GPS post processing statistics for first set of survey data collected during the week of 10/2/00 by Richard Ortt, Jr., and Harold Catlett. The points referenced are identified below. 28TH PK nail near water level recorder at Bayshore Estates (27th Street Ocean City) GPS reference benchmark established by U.S. Army Corps of Engineers, located in Ocean BM02 Pines Community Marina MH01 Manhole cover at Marsh Harbor NGS HARN BM located on Assateague Island in National Park, directly across Sinepuxent North_Beach_2 Bay from South Pt.

Statistics Network Adjustment in WGS84. Number of baselines 5 Number of terrestrial measurements 0 Geoidmodel Northeastern US NOAA96 Number of control points in WGS84 2 Number of adjusted points 4 Confidence level 1 Sigmas Significance level for tau test 1.00 % Standard error of unit weight 0.988 Number of iterations 1

1. Baselines Input in WGS84 (Components and Std.Dev.)

Baseline DX [m] DY [m] DZ [m] sDX [mm] sDY [mm] sDZ [mm] 28TH-BM02 -4239.455 920.065 2498.761 13.0 36.8 30.1 28TH-North_Beach_2 -3253.395 -12173.619 -13851.061 12.7 36.3 29.5 BM02-North_Beach_2 986.054 -13093.720 -16349.780 4.7 8.8 7.4 BM02-MH01 3217.260 -3631.812 -5478.191 14.3 29.0 30.1 MH01-North_Beach_2 -2231.242 -9461.863 -10871.665 11.2 23.4 24.8 Baselines which were rejected by the statistical test are marked.

2. WGS84 Control Points Input (Cart. Coordinates and Std.Dev.)

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Point X [m] Y [m] Z [m] sX [mm] sY [mm] sZ [mm] BM02 1284753.458 -4838172.089 3939176.730 0.0 0.0 0.0 North_Beach_2 1285739.507 -4851265.800 3922826.939 0.0 0.0 0.0

3. Adjusted Baselines in WGS84 (Components and Std.Dev.)

Baseline DX [m] DY [m] DZ [m] sDX [mm] sDY [mm] sDZ [mm] 28TH-BM02 -4239.449 920.078 2498.745 9.0 25.5 20.8 28TH-North_Beach_2 -3253.400 -12173.632 -13851.046 9.0 25.5 20.8 BM02-North_Beach_2 986.050 -13093.710 -16349.791 0.0 0.0 0.0 BM02-MH01 3217.279 -3631.834 -5478.152 8.7 18.0 18.9 MH01-North_Beach_2 -2231.230 -9461.876 -10871.638 8.7 18.0 18.9

4. Baseline Corrections (Corrections and Normalized Corrections)

Baseline vN [mm] vE [mm] vH [mm] vN/sN vE/sE vH/sH 28TH-BM02 -5.0 8.7 -19.0 -0.7 0.7 -0.6 28TH-North_Beach_2 4.6 -8.3 18.2 0.7 -0.7 0.6 BM02-North_Beach_2 -2.3 -1.8 -15.1 -1622.5 -1279.0 -10824.7 BM02-MH01 14.7 12.9 44.4 1.8 1.9 1.7 MH01-North_Beach_2 10.4 8.4 28.9 1.3 1.3 1.1 Baselines which were rejected by the statistical test are marked.

5. Adjusted Points in WGS84 (Cart. Coordinates and Std.Dev.)

Point X [m] Y [m] Z [m] sX [mm] sY [mm] sZ [mm] 28TH 1288992.907 -4839092.168 3936677.984 9.0 25.5 20.8 BM02 1284753.458 -4838172.089 3939176.730 0.0 0.0 0.0 MH01 1287970.737 -4841803.923 3933698.577 8.7 18.0 18.9 North_Beach_2 1285739.507 -4851265.800 3922826.939 0.0 0.0 0.0

6. Adjusted Points in WGS84 (Geogr. Coordinates and Std.Dev.)

Point Lat [Deg] Lon [Deg] ell.H [m] orth.H [m] geoid.H [m] sN [mm] sE [mm] sH [mm] 28TH N38° 21' 29.54327'' W75° 05' 03.87548'' -34.246 1.733 -35.979 7.1 12.6 30.9 BM02 N38° 23' 12.91505'' W75° 07' 42.91693'' -34.459 1.480 -35.939 0.0 0.0 0.0 MH01 N38° 19' 26.32401'' W75° 06' 13.27522'' -33.382 2.632 -36.014 8.3 6.7 25.4 North_Beach_2 N38° 11' 57.30665'' W75° 09' 21.86176'' -34.702 1.465 -36.167 0.0 0.0 0.0

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7. Adjusted Points in Local System (Plane Coordinates and Std.Dev.)

Point N [m] E [m] ell.H [m] sN [mm] sE [mm] sH [mm] 28TH 0.000 -0.000 -34.246 7.1 12.6 30.9 BM02 3188.305 -3859.782 -34.458 0.0 0.0 0.0 MH01 -3799.165 -1685.723 -33.383 8.3 6.7 25.4 North_Beach_2 -17641.711 -6277.246 -34.741 0.0 0.0 0.0 Radius of the Reference Sphere is 6372000.000 m. System origin is point 28TH.

8. Adjusted Points Error Ellipses

Point A [mm] B [mm] Angle [Deg] 28TH 12.7 6.9 -81.8 BM02 0.0 0.0 0.0 MH01 8.4 6.6 -13.8 North_Beach_2 0.0 0.0 0.0

Table 20. GPS post processing statistics for second set of survey data collected during the week of 10/2/00 by Richard Ortt, Jr., and Harold Catlett. The points referenced are identified below. 125S PK nail on Ocean City Recreation Pier at 125th Street in Ocean City

BM02 GPS reference benchmark established by U.S. Army Corps of Engineers, located in Ocean Pines Community Marina KW01 PK nail on road near bulkhead in Keenwick Community

North_Beach_2 NGS HARN BM located on Assateague Island in National Park, directly across Sinepuxent Bay from South Pt From: Ashtech Office Suite for Survey 2.00, Copyright (C) 1997 - 1999 by Ashtech Inc., 10/4/2000, 3:28:25 PM

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1. Baselines Input in WGS84 (Components and Std.Dev.)

Baseline DX [m] DY [m] DZ [m] sDX [mm] sDY [mm] sDZ [mm] 125S-BM02 -4757.436 -4495.004 -3934.581 9.0 19.4 13.3 125S-North_Beach_2 -3771.374 -17588.711 -20284.366 11.6 25.1 17.3 BM02-North_Beach_2 986.054 -13093.721 -16349.780 4.7 8.8 7.4 BM02-KW01 2239.241 5741.653 6268.870 12.5 18.6 19.7 KW01-North_Beach_2 -1253.159 -18835.411 -22618.601 15.7 23.5 24.7 Baselines which were rejected by the statistical test are marked.

2. WGS84 Control Points Input (Cart. Coordinates and Std.Dev.)

Point X [m] Y [m] Z [m] sX [mm] sY [mm] sZ [mm] BM02 1284753.458 -4838172.089 3939176.730 0.0 0.0 0.0 North_Beach_2 1285739.507 -4851265.800 3922826.939 0.0 0.0 0.0

3. Adjusted Baselines in WGS84 (Components and Std.Dev.)

Baseline DX [m] DY [m] DZ [m] sDX [mm] sDY [mm] sDZ [mm] 125S-BM02 -4757.431 -4495.003 -3934.579 6.5 14.1 9.7 125S-North_Beach_2 -3771.381 -17588.713 -20284.370 6.5 14.1 9.7 BM02-North_Beach_2 986.050 -13093.710 -16349.791 0.0 0.0 0.0 BM02-KW01 2239.228 5741.671 6268.847 9.0 13.4 14.2 KW01-North_Beach_2 -1253.178 -18835.382 -22618.637 9.0 13.4 14.2

4. Baseline Corrections (Corrections and Normalized Corrections)

Baseline vN [mm] vE [mm] vH [mm] vN/sN vE/sE vH/sH 125S-BM02 1.5 4.8 1.3 0.2 0.7 0.1 125S-North_Beach_2 -2.5 -8.1 -2.2 -0.3 -1.1 -0.1 BM02-North_Beach_2 -1.7 -2.0 -15.7 -1291.9 -1521.2 -12076.2 BM02-KW01 -5.0 -7.2 -31.1 -0.6 -1.0 -1.7 KW01-North_Beach_2 -7.7 -11.5 -49.4 -0.9 -1.6 -2.7 Baselines which were rejected by the statistical test are marked.

5. Adjusted Points in WGS84 (Cart. Coordinates and Std.Dev.)

Point X [m] Y [m] Z [m] sX [mm] sY [mm] sZ [mm] 125S 1289510.889 -4833677.087 3943111.308 6.5 14.1 9.7 BM02 1284753.458 -4838172.089 3939176.730 0.0 0.0 0.0 KW01 1286992.686 -4832430.418 3945445.576 9.0 13.4 14.2 North_Beach_2 1285739.507 -4851265.800 3922826.939 0.0 0.0 0.0

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6. Adjusted Points in WGS84 (Geogr. Coordinates and Std.Dev.)

Point Lat [Deg] Lon [Deg] ell.H [m] orth.H [m] geoid.H [m] sN [mm] sE [mm] sH [mm] 125S N38° 25' 55.77141'' W75° 03' 45.77061'' -34.898 1.008 -35.906 7.4 7.1 15.2 BM02 N38° 23' 12.91505'' W75° 07' 42.91693'' -34.459 1.480 -35.939 0.0 0.0 0.0 KW01 N38° 27' 32.43115'' W75° 05' 12.87200'' -34.936 0.934 -35.870 8.5 7.3 18.4 North_Beach_2 N38° 11' 57.30665'' W75° 09' 21.86176'' -34.702 1.465 -36.167 0.0 0.0 0.0

7. Adjusted Points in Local System (Plane Coordinates and Std.Dev.)

Point N [m] E [m] ell.H [m] sN [mm] sE [mm] sH [mm] 125S 0.000 -0.000 -34.898 7.4 7.1 15.2 BM02 -5019.512 -5755.312 -34.457 0.0 0.0 0.0 KW01 2980.735 -2111.766 -34.936 8.5 7.3 18.4 North_Beach_2 -25848.953 -8177.705 -34.789 0.0 0.0 0.0 Radius of the Reference Sphere is 6372000.000 m. System origin is point 125S.

8. Adjusted Points Error Ellipses

Point A [mm] B [mm] Angle [Deg] 125S 7.5 7.0 28.2 BM02 0.0 0.0 0.0 KW01 8.7 7.1 21.6 North_Beach_2 0.0 0.0 0.0

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Appendix B Knudsen operating parameter settings

Table 20. Knudsen echosounder system control settings used for the hydrographic surveys conducted for this study. Global control settings Low frequency (LF) High frequency (HF) settings settings Range 0 Power 1 Power 1 Phase 1 AGC On AGC On Autophase Off GAIN 32 GAIN 48 Timed event On Processing 5 Processing Gain 0 marks Gain Interval 50 Sensitivity Off Sensitivity Off seconds Units Meters Tx Blank 9 Tx Blank 3 TVG Off Pulse 1 Pulse 0 Gatewidth 2 Primary HF Channel Ping interval 500 millisec. (ms)

The setting parameters are defined as follows: Range- sets the transmit blanking distance used by the echosounder's internal digitizer to avoid false triggering on transmit reverberation. Phase- selects the depth, or location in the water column, of the active window Autophase- If ON, the phase changes are performed automatically in response to information provided by the primary channel bottom tracking algorithm. Timed event marks- if ON, allows the user to select the echosounder's internally timed event marks. The echosounder will cause internally generated event mark at the time interval selected in the Timed Event Interval box. Interval- Sets interval (seconds) for timed event marks on the echogram. Units- Operating units, can be meters, feet, or fathoms TVG- Time varied gain) on the analog receivers. The OFF setting provides constant receive gain throughout each pulse-echo cycle (note that receive gain will vary from ping to ping if AGC is on). Gatewidth- The gate width is a depth variability tolerance value used by the bottom tracking algorithm to determine the validity of the current depth value. The value is defined as a distance above or below the bottom depth trend established by the current and several previous readings. If the most

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current depth reading falls within this range, it is considered valid. If a depth return falls outside of this range, it is deemed invalid and “0.0" is displayed in all the dialogue boxes with depth displays. Primary Channel- The Primary Channel parameter defines the frequency channel used as the reference depth for the auto phasing algorithm. The Primary Channel designation only has effect when both channels of a dual-channel echosounder are ON. Ping interval- Sound pulse rate in milliseconds Power- Specifies the transmit power level of the pulse being transmitted. AGC- Invokes automatic gain control of the analog receive gain Gain- Controls the analog receiver gain of the relevant channel. Processing Gain- Provides for additional gain in the digital signal processing software which can be used with very low level signals. Sensitivity- Parameter that controls the minimum echo strength acceptable by the bottom detection software. This parameter is useful in areas where soft sediments overlay harder materials, and where buried layers may often produce stronger echoes than the real bottom. If Sensitivity is OFF (the default condition), the bottom detection software will always select the strongest echo in the window . Increasing the Sensitivity causes the bottom detection software to accept a weaker but shallower echo. The higher the Sensitivity, the weaker the echo, relative to the strongest echo in the window, that will be selected. Tx Blank- Sets the transmit blanking distance used by the echosounder's internal digitizer to avoid false triggering on transmit reverberation. Pulse- Pulse type

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Appendix C MathCAD Splining Process for interpolating water level adjustment

1. MathCAD routine for interpolating water levels for given times. The output was used to synchronize all water level and tide data.

1. Read Data from Files. OUTPUTTIMES := Q:\..\may2time.txt Desired Output Times (times from soundings files) INPUTDATA := Q:\..\iofwobs.txt Measured Tidal Data (time, Water Level) 2. Simplify the names of the Arrays for writing program. A := OUTPUTTIMES B := INPUTDATA 3. Sort the measured tidal data according to time (should already be done). B := csort(B, 0) 4. Break out the measured data into separate vectors (one dimensional arrays). á ñ X := B 0 Time Array á ñ Y := B 1 Level Array 5. Spline the set of data using cubic splining techniques. S := cspline( X, Y) CSpline of the level data 6. Interpolate the splined data to the desired time elements. LEVEL := interp(S, X, Y, A) Interpolate Level data 7. Save Results to Text File.

Q:\..\may2tide.txt LEVEL

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2. MathCAD routine for interpolating water levels for times of soundings data using weighted factor based on distance sounding was between tide stations. The output was used to adjust the Sinepuxent Bay sounding data to NAVD88.

1. Read Data from Files. OUTPUT := Q:\..\jun1.txt Desired Output Times and Northings (times and Northings from soundings files) INPUTDATA1 := Q:\..\southptide.txt Measured Tidal Data (time, Water Level) of Southern most station (South Point) INPUTDATA2 := Q:\..\snugtide.txt Measured Tidal Data (time, Water Level) of Middle station (Snug Harbor) Measured Tidal Data (time, Water Level) of Northern most station (Marsh Harbor) INPUTDATA3 := Q:\..\mhtide2.txt 2. Specify Northing Coordinates for Tidal Stations. (UTM -- NAD 83 -- Meters) STATION0,0 := 4229841 Measured Tidal Station Northings Used for weighted average adjustments. STATION0,1 := 4238318

STATION0,2 := 4241781 3. Compute Distances between Tidal Stations. Meters. DIS01 := STATION0,0 - STATION0,1 Computed Distances between tide stations for weighted average normalization. DIS12 := STATION0,1 - STATION0,2

DIS02 := STATION0,0 - STATION0,2 4. Simplify the names of the Arrays for writing program. á ñ A := OUTPUT 0 B := INPUTDATA1 C := INPUTDATA2 D := INPUTDATA3 á ñ E := OUTPUT 1 5. Sort the measured tidal data according to time (should already be done). B := csort(B, 0)

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C := csort(C, 0) D := csort(D, 0) 6. Break out the measured data into separate vectors (one dimensional arrays). á ñ BX := B 0 Time Array á ñ BY := B 1 Level Array á ñ CX := C 0 á ñ CY := C 1 á ñ DX := D 0 á ñ DY := D 1 7. Spline the set of data using cubic splining techniques. S := cspline(BX, BY) T := cspline(CX, CY) CSpline of the level data U := cspline(DX, DY) 8. Interpolate the splined data to the desired time elements. LEVEL1 := interp(S, BX, BY, A) LEVEL2 := interp(T, CX, CY, A) Interpolate Level data LEVEL3 := interp(U, DX, DY, A) LEVELI := augment(LEVEL1, LEVEL2, LEVEL3) Create one array from all levels. 9. Develop interpolated value at sounding location based upon linear spline of measured tides. Transpose array T TIDE := LEVELI N := last(E) Set range for operations. i := 0, 1.. N Linear spline of data á ñ T á ñ V i := cspline(STATION , TIDE i ) áiñ T áiñ LEVEL4i := interp(V , STATION , TIDE , Ei) Interpolate level from northing of sounding. 10. Develop interpolated value at sounding location based upon distance weighting of measured tides. j := 0, 1.. N Set range of operations. WEIGHT0, j := 0

WEIGHT1, j := 0 Set default weight to zero.

WEIGHT2, j := 0 Set range of operations. k := 0, 1.. N

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Set all points north of northern most station to use only northern most data. WEIGHT2, k := if(Ek ³ STATION0,2, 1, 0) Set all points south of southern most station to use only southern most data.

WEIGHT0, k := if(Ek £ STATION0,0, 1, 0) é æ Ek - STATION0,1 ö ù WEIGHT2, k := ifê(Ek < STATION0,2) Ù (Ek > STATION0,1) , ç ÷ , WEIGHT2, kú ë è DIS12 ø û é é é(Ek - STATION0,1)ùù ù WEIGHT1, k := ifê(Ek < STATION0,2) Ù (Ek > STATION0,1) , ê1 - ê úú , WEIGHT1, kú ë ë ë DIS12 ûû û é æ Ek - STATION0,0 ö ù WEIGHT0, k := ifê(Ek £ STATION0,1) Ù (Ek > STATION0,0) , ç ÷ , WEIGHT0, kú ë è DIS01 ø û é é é(Ek - STATION0,0)ùù ù WEIGHT1, k := ifê(Ek £ STATION0,1) Ù (Ek > STATION0,0) , ê1 - ê úú , WEIGHT1, kú ë ë ë DIS01 ûû û l := 0, 1.. N Set range of operations. Perform Dot product by row of Weight matrix by water level matrix to get weighted value. álñ álñ LEVEL5l,0 := (WEIGHT) ×TIDE 11. Combine all time interpolated tide levels into one 5 column array. (MarshHarbor, SnugHarbor, SouthPoint, Splined Calculation, Weighted Calculation) LEVEL := augment(LEVEL1, LEVEL2, LEVEL3, LEVEL4, LEVEL5) 12. Save Results to Text File.

Q:\..\jun1out.txt LEVEL

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Appendix D Final XYZ Sounding Data

Final depths, adjusted to NAVD88 are contained in four files, in ASCII, comma delimited format. Each row represents one sounding, and consists of three variables: Northing (UTM, NAD83, Meters), Easting (UTM, NAD83, Meters), and Elevation (NAVD88, Meters). There is no header row. The files are included on CD-ROM with this report

File Name Area No. of rows (soundings) AssawXYZ.dat Assawoman Bay 148,626 NewportXYZ.dat Newport Bay 76,372 SinepuxXYZ.dat Sinepuxent Bay 161,134 StMarXYZ.dat St. Martin River 67,936

NCBBathymetadata.doc Metadata for XYZ sounding data in MSWord format NCBBathymetadata.rtf Metadata for XYZ sounding data in Rich Text format

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