Dredge Surveys

A detailed survey of a specific area (usually a 1 to 2 mile section) of the river. Dredge surveys can be split into two groups: pre-dredge surveys and post-dredge surveys. Pre-dredge surveys are analyzed to determine if dredging is required in a potentially problematic location. If dredging is required, these surveys are then used to layout the dredge cuts and to estimate the volume of material that will need to be moved. A post-dredge survey is completed after dredging has been completed in a specific location to ensure that the problematic area has been removed.

Survey depths are shown below a reference plane representing a low flow condition.  St. Louis District has two types of river systems, a pooled river created by the Lock and Dam system, and an open free flowing river without Locks and Dams.  In a pooled river system, the low flow condition is determined from the minimum water surface provided by the Lock and Dam system; this water surface is known as minimum pool.  In an open or free flowing river, such as the Mississippi River downstream of Locks 27, the low flow condition is called the Low Water Reference Plane (LWRP). The low flow condition the LWRP represents is the calculated water surface profile resulting from the 97% exceedance discharge based on a set period of record. This reference plane allows for common comparison between different points on the river. 

The most recent surveys are linked below.  Older surveys can be found by going to the USACE e-hydro website, where all available surveys are posted.

E-Hydro Link