Watersheds are basin-like landforms defined by highpoints
and ridgelines that descend into lower elevations and stream valleys. Even
in the relatively flat topography of East Baton Rouge Parish, there are
ridgelines that form boundaries between watersheds. The East Baton Rouge
Parish is within the Lake Pontchartrain Basin, and the Lower Mississippi
Within a watershed, the natural and built systems capture and move
precipitation, filter and store water, and control its release over time.
Impervious surfaces – anything that prevents rainfall from soaking into the
ground, such as buildings, roads, or parking lots – have a significant
impact on the watershed functioning because they prevent infiltration and
increase stormwater runoff. Watersheds are nested systems meaning that many
small watersheds make up the larger regional watershed. The hydrology of the
Parish naturally divides into three main watersheds, which are subdivided
into a total of 704 micro-watersheds.
The eastern part of the Parish drains into the Amite River and the southern
part of the Parish drains into Bayou Manchac. The northwest portion of the
Parish drains into the Mississippi River. Water management and management of
biodiversity and other natural systems, is best handled at the watershed
level. Remediation or mitigation of such changes, therefore, should take
place within the same watershed to achieve ecological benefits and maintain
the integrity of the watershed.
Under the Clean Water Act, waterways on the Impaired Waterbodies List must
undergo watershed modeling to assess the loads of each pollutant for which
they are listed. Termed “Total Maximum Daily Loads” (TMDLs), these models
calculate the reduction in the pollutant that will be necessary for the
waterway to be removed from the Impaired Waterbodies List. TMDL calculations
performed in the Pontchartrain Basin so far have resulted in substantial
reductions in pollutant loads.
In addition, under the Clean Water Act, urban areas are mandated to meet
standards of the Environmental Protection Agency (EPA) Municipal Separate
Storm Sewer Systems (MS4) Program. The MS4 Program requires that urban areas
eventually monitor their stormwater discharges as a point source of
pollution. Water quality limits must be set on these discharges and urban
areas are responsible for meeting the limits.