/ Maryland, Virginia, and Pennsylvania, USA, have agreed to reduce nutrient loadings to Chesapeake Bay by 40% by the year 2000. This requires control of nonpoint sources of nutrients, much of which comes from agriculture. Riparian forest buffer systems (RFBS) provide effective control of nonpoint source (NPS) pollution in some types of agricultural watersheds. Control of NPS pollution is dependent on the type of pollutant and the hydrologic connection between pollution sources, the RFBS, and the stream. Water quality improvements are most likely in areas of where most of the excess precipitation moves across, in, or near the root zone of the RFBS. In areas such as the Inner Coastal Plain and Piedmont watersheds with thin soils, RFBS should retain 50%-90% of the total loading of nitrate in shallow groundwater, sediment in surface runoff, and total N in both surface runoff and groundwater. Retention of phosphorus is generally much less. In regions with deeper soils and/or greater regional groundwater recharge (such as parts of the Piedmont and the Valley and Ridge), RFBS water quality improvements are probably much less. The expected levels of pollutant control by RFBS are identified for each of nine physiographic provinces of the Chesapeake Bay Watershed. Issues related to of establishment, sustainability, and management are also discussed.Research is sometimes applied to broad-scale environmental issues with inadequate knowledge or incomplete understanding. Public policies to encourage or require landscape management techniques such as riparian (streamside) management will often need to proceed with best professional judgment decisions based on incomplete understanding.Riparian forest buffer systems (RFBS) are streamside ecosystems managed for the enhancement of water quality through control of nonpoint source pollution (NPS) and protection of the stream environment. The use of riparian management zones is relatively well established as a best management practice (BMP) for water quality improvement in forestry practices (Comer-

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This article presents the elements involved in the design of a bioretention planter/trench infiltration-detention system as part of a very large-scale urban retrofit project. The prototype system was designed to intercept all of the runoff from a synthetic 5.08-mm 24-h rainfall event. Diverted flows were conveyed into bioretention planter for treatment. The bioretention systems were fingerprinted into areas comprising 0.8% of the contributory drainage areas, with an associated stone trench comprising another 3.4%. As layered systems, an approach that is capable of modeling vertical flows in addition to dynamic routing of outflows is used. The system was first modeled using HydroCAD, a design storm event modeling software. A four-compartment node system is used to model the dynamics of flow through the layers. The system was then modeled using SWMM 5.0.014 continuous simulation software. The resulting response to a design storm was computed by both of these models to compare the results of each method. The resulting SWMM model was then run on the 2005 design year rainfall distribution. Under existing conditions, over 60% of annual runoff volume exceeded the 3.50 L • s −1 •ha −1 ͑0.05 cfs-ac −1 ͒ threshold for initiation of combined sewer overflows ͑CSOs͒. Nearly all runoff was intercepted by the planter/trench infiltration system and even with a soil infiltration rate of only 2.54 mm• h −1 , 47% was infiltrated, and less than 6% was discharged at rates that could initiate CSOs. The number of CSO exceedance pulses was reduced from 233 to 6, a reduction of 97%. The volume of flows exceeding the CSO threshold decreased by 90% in the planter/trench system.