Lake Mauvaise Terre Streambank Erosion & In-lake Dam Assessment

Synopsis

Lake Mauvaise Terre is located in Morgan County, Illinois and is a water supply for the City of Jacksonville. A previous plan developed by Northwater identified the need for a direct assessment of streambank erosion to more accurately quantify watershed nutrient and sediment loading and identify in-stream treatment opportunities. The plan also identified a in-lake dam as an effective strategy for improving water quality; a feasibility study was needed to move forward and answer additional questions form City officials.

Client(s):

American Farmland Trust, City of Jacksonville, IL
Services:

Geosciences & Engineering, Water Resources, Water Supply
Market/Sector:

Agriculture, Government
Location:

Jacksonville, Illinois

Project Description

Lake Mauvaise Terre is located in Morgan County, Illinois and is a water supply for the City of Jacksonville. It is impaired for numerous constituents, including phosphorus and sediment. To compliment recent work on a Watershed Implementation Plan, Northwater was retained by the American Farmland Trust (AFT) and the city to perform a reach level assessment of watershed streambank erosion and to evaluate the potential for construction of a new in-lake/low-flow sediment dam.

Northwater surveyed over 13 miles of streams to quantify lake sediment and nutrient loads associated with bank erosion and to identify potential project locations. It was determined that an in-lake/low flow dam to trap sediment is feasible and that that streambank erosion is responsible for 12% of the total watershed sediment load. Northwater concluded that efforts to limit sediment loading from upland areas would result in much greater benefits to water quality. Project recommendations and a map atlas representing results of the stream survey were developed. The entire project was completed on time under a very aggressive schedule.