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Minnesota Stormwater Manual

Literature review summary for Unified Sizing Criteria
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6. Literature review summary

Channel enlargement/erosion is the result of changes in runoff distribution and lower watershed sediment yield. This paper compares peak rate control to sediment yield control methods and evaluates erosion potential using five sediment transport equations. The major finding is that both control methods increase the duration of lower flows and cause changes that would result in increased channel erosion. Additionally, the use of detention ponds reduces the sediment load to the stream and can cause further degradation of the stream bed. The author’s recommendation is to evaluate the impact of reductions in sediment load and to match the “shape and magnitude of the predevelopment hydrograph over a range of geomorphically important flows”.
This paper summarizes modeling indicating that similar erosion protection for streams is provided by extended detention of the 1 year 24 hour storm and the “distributed runoff control” method (the method recommended by MacRae, 1993). The methods provide protection for storms of less than 2 inches; for larger rainfall, the two methods are the same as peak rate control. The paper also summarized a study of specific stream reaches and found that site specific morphologic studies are necessary to fully evaluate stormwater management needs They recommend a three step process of assessing geomorphic conditions, determining stability thresholds, and determining allowable stormwater release.
The authors found that recurrence interval for bankfull flow (effective discharge) for Illinois streams was less than 1.1 years for each of the about 20 streams analyzed.
  • Ferguson, B.K. and T. Deak, 1994. Role of Urban Storm-Flow Volume in Local Drainage Problems. Jour. of Water Resources Planning and Management (ASCE), 120(4): 523-530.
This study shows that the increase in runoff volume alone can cause increases in flooding where restrictions in flow occur. The recommended solution is the use of infiltration instead of detention as a management practice.
The authors found that erosion potential can be predicted with probability density functions (PDFs) of channel velocity and duration of flows.
The authors report that streams in wetland environments show different bankfull characteristics than non-wetland alluvial streams. Bankfull cannot be defined the same way for wetland streams as for non-wetland streams.
This paper uses two-dimensional stream scour analysis to evaluate effect of peak rate control and “over-control” (detention that allows sediment transport rate to remain at predevelopment levels). Neither successfully maintained pre-development sediment transport to a level that would not cause scour or aggradation of the channel. The author’s recommendation is to use a third method called “distributed runoff control” that follows the over-control method but also allows larger flows through to make use of the floodplain and limit erosion within the channel.
The author reports that peak rate control to the 2-year event increases mid-bankfull events that are most important for erosion control of streams in urbanized areas. The author’s model indicated that the duration of mid-bankfull flow increased by 4 to 10 times as the level of development increased even though rate control facilities were in place.
The authors found that stormwater management using detention only causes changes in the timing of storage and increases in volume. These changes cause increases in the duration of bankfull flows which lead to stream erosion. Detention basins do not adequately mimic natural storage, do not result in similar stream sediment transport patterns or bankfull flow durations, and can have a regional impact downstream of the facility. The authors’ recommendation is to use storage that is distributed spatially throughout a site and releases water distributed over time while also reducing the runoff volumes.
  • McCuen, R.H. and G.E. Moglen, 1988. Multicriterion Stormwater Management Methods. Jour. of Water Resources Planning and Management (ASCE), 114(4): 414-431.
This paper provides design methods for channel and erosion based criteria for stormwater management. It emphasizes that multiple criteria are needed to ensure that the problem to be addressed by stormwater management is adequately solved. The paper demonstrates that peak rate control alone does not address the issue of channel erosion.
The authors report that infiltration basins distributed over a watershed provide peak rate control up to 30% (based in this case on a subwatershed equivalent CN reduction of 5 for each subwatershed with an infiltration basin). The incremental inclusion of new BMPs can result in an equally good solution to an initial determination of all optimal locations for BMPs, as long as the basins are installed in highly developed areas.
The authors found that the assumption of 1.5- to 2-year recurrence interval for bankfull flow is inappropriate to Midwestern streams and rivers. The paper evaluates bankfull flow in Ohio streams and finds a range between 0.3 and 1.5-year as the recurrence intervals corresponding to bankfull flow. Assuming a 1.5 to 2-year recurrence interval for bankfull flow will result in incised channels if it is inappropriate to the stream in question. The authors’ recommendation is to evaluate the specific stream to determine the bankfull flow and recurrence interval.
  • Rohrer, C.A and L.A. Rosner, 2006. Matching the Critical Portion of the Flow Duration Curve to Minimize Changes in Modelled Excess Shear. Water Science and Technology, 54(6-7): 347- 354.
The authors propose to manage stream erosion by determining the critical flow causing streambed erosion and control flows only above that level to match critical portions of the flow duration curve. Urbanization increases runoff volume unless volume reductions are implemented. Without volume reductions, the duration of flows will increase regardless of the type of detention used. This study indicates that if the duration of flows above the critical threshold for erosion of the bed and bank remains the same, erosion of the channel will not increase. Changes in sediment supply from the watershed, however, could alter the threshold for erosion in the stream. For highly erodible channels the flow duration curve needs to be matched entirely from pre- to post-development to prevent channel erosion. The study suggests that reducing the total volume of runoff “may provide a better method for stormwater management for watersheds that drain to fine grained non-cohesive or erodible clay streams.”
  • Shields, F.D., R.R. Copeland, P.C. Klingeman, M.W. Doyle and A. Simon, 2003. Design for Stream Restoration. Jour. of Hydraulic Engineering (ASCE), 129(8): 575-584.
The authors define channel-forming discharge, bankfull discharge and return-interval discharge and describe how to use these concepts in stream restoration.
This paper provides an overview of basic streamflow concepts.
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