As a mainstay of our work, single beam bathymetry uses an echo sounder to measure depths under the survey vessel. Tide and other factors are accounted for to produce data referenced to the appropriate datum. With proper calibration, the data is reliable and relatively inexpensive to collect. A dual frequency system is used to “see through” fluid mud or into the surface of the sea floor. Often, changes in the sea floor composition can be detected.
Equipment: Knudsen, ODOM CVM, or Hydrotrac
Multibeam bathymetry measures depths in a swath perpendicular to the direction that the survey vessel is traveling. The width of the swath is often twice the water depth or greater. When detailed knowledge of the bottom and its features are needed, multibeam provides a robust solution. Sand waves, trenches and structures can all be seen with multibeam.
Equipment: R2Sonic 2024, ODOM MB2, or Reson TP-50
Vibracores, drop tube samples, grab samples, and other methods are employed to obtain sediment samples for a variety of projects. Ground truthing sub-bottom profile surveys or sampling for dredging projects are our most common sampling projects.
Another mainstay of our work, side scan sonar is an extremely efficient method to map the surface of the sea floor. Items from the size of a paint can to a sunken ship can be detected and mapped. side scan sonar is often used in conjunction with multibeam bathymetry to assist in identifying features on the sea floor. Seagrass, oyster reefs and other natural features can be detected. Man-made objects that are lost or present a hazard are located and mapped using side scan sonar.
A magnetometer is one of the most reliable methods to locate unknown ferrous objects on or under the sea floor. Normally used for locating pipelines and wrecks it has become common for dredging or pipeline projects.
When details of the structure of the sea floor are required we often turn to sub-bottom profiling. A “chirp” signal in the 2 to 24k Hz range is typically used to produce a two-dimensional profile of the sea floor. Sand, mud, organic, oyster shell and other layers can be mapped. Core data and other geotechnical information are often used to correlate layers and determine the composition of the sea floor.
Oysters are critical to the health of our bays and estuaries. Oyster surveys are conducted using TPWD specification dredges, core, and other sampling techniques. Reports include oyster, bay bottom, and substrate. Often there is a cost savings when we are tasked with hydrographic surveying as well as sensitive resource surveys.
Seagrass is a nursery habitat for shrimp, crabs, fish, and other wildlife. Naismith Marine conducts sensitive resource surveys used in the Corps permitting process. Seagrass surveys report the absence or presence of seagrass, species, and, density of the seagrass bed. Often there is a cost savings when we are tasked with hydrographic surveying as well as sensitive resource surveys.
Naismith Marine conducts wetland delineations according to methods approved by the US Army Corps of Engineers (USACE). The area and extent of both wetlands and uplands are delineated within the survey area. Naismith can also conduct High Tide Line (section 404 Jurisdictional Limit in the absence of wetlands) and Mean High Water Line (Section 10 Jurisdictional Limit) delineations. Naismith can also coordinate with USACE to obtain approval for delineations of potentially jurisdictional areas.
Tide and wave action is critically important to coastal facilities. We can deploy and monitor electromagnetic current meters (single point) and Acoustic Doppler Current Profilers (profile). Over-the-side deployment may be useful in inlets and other waterways. We can detect and measure infragravity waves related to storm events. Temporary tide gauges can be installed on existing structures or we can drive small pile structures.
Equipment: Valeport, Sontek, Custom tide gauges
Naismith Marine works with the top coastal engineering firms to support the permit process. Wetland delineation, jurisdiction, oyster, seagrass, and other surveys are routine. We can assist landowners and commercial interest through the permit process for docks, piers, bulkheads, pipelines, wells and other small projects that do not require engineering.
Naismith Marine provides, vessel, side scan sonar, sub-bottom, and dive support for marine archaeologists. Some projects in Texas bays require a cultural resource survey as part of the USACE permitting process. The marine archaeologist runs the data collection from our vessel. We supply the expertise needed to collect data exactly to his or her guidelines meeting all of the THC & USACE requirements.
Naismith maintains a small dive team for inspections, debris ID and removal, and installation / maintenance of various instrumentation
Safe navigation depends on knowing what may present a hazard and removing any potential problems.
Infrastructure monitoring depends on knowing what is under the water as well as above.
3d scanning is used for determining size and location of underwater structural members
Sector scanning can be horizontal or vertical to provide an image of the overall structure. Often in support of dive inspections to show location and large scale features
Multibeam, Side Scan Sonar, and Diving are used to assist with the construction and monitoring of artificial reefs. Reefs range from shallow oyster reefs to ships sunk in the Gulf of Mexico