Bathymetry Survey for Lakes and Ponds

Many of our new customers are not familiar with bathymetry surveys—what they are, what their purpose is, and what the end result of the survey should look like.

The bathymetry survey provides critical information about your pond or lake that is pertinent for several different reasons.

• First and foremost, the bathymetry survey gives you a clear understanding of your water body’s health and overall condition.
• The bathymetry report helps your pond or lake management provider to develop an appropriate dredge schedule. It also provides capacity levels that are necessary for calculating herbicide, pesticide and algaecide treatments.
• The data provided through a bathymetry report is also necessary for obtaining Audubon Society certifications, NPDES and stormwater permits and other similar certifications/permits.

What Is a Bathymetry Survey?

A bathymetry survey is a hydro-acoustic survey of a lake, pond or other water body from which a series of maps is produced. These maps can be used to determine:

• How much sediment is in the water body (sediment volume)
• Where the sediment is located (sediment placement)
• How much dredging is needed and where
• Appropriate ratios for chemical water treatments

How Is a Bathymetry Survey Conducted?

Most of our bathymetry surveys are performed using either an airboat or a kayak unit, depending on the size and accessibility of the water body. The surveying equipment is mounted onto the vessel and a one-man crew performs the operation.

The actual survey process consists of the boat or kayak moving very slowly across the water body, typically in a grid pattern to ensure the creation of the most accurate map possible.

We can typically survey approximately 10 acres of a pond or lake in a day.

What Is a Bathymetry Report?

Once the survey has been completed, we will produce a bathymetry report consisting of several maps and images of the water body. These include:

• A contour map that shows the depth of the pond from the top of the water to the top of the sediment at all points
• A composition map that shows the thickness or density of each sediment deposit; this information helps us determine how much time it will take to dredge each portion of the pond or lake
• A thermal image that helps us identify the types of sediment in the water as well as sediment volume
• A capacity report that helps us determine the water body’s diminished capacity, which must be kept within a certain range (typically 25 to 30%) per state and/or county regulation

Ultimately, the bathymetry report helps us develop a detailed dredge proposal and schedule that will keep the water body in compliance with diminished capacity regulations as well as help it remain as healthy as possible.

How Often Is a Bathymetry Survey Needed?

The answer depends on the type and function of your particular water body. A general rule of thumb for most ponds and lakes is to conduct a bathymetry survey every five years. This will help you keep abreast of sediment buildup within the water as well as other potential issues, such as fish structures.

On the other hand, many retention ponds see drastic changes in sediment levels over a shorter period of time. In these cases, a bathymetry survey every one to two years may be ideal.

We also recommend conducting a bathymetry survey after any major storm event, such as a hurricane or severe tropical storm that inundates the water body.

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