Mardella Branch Stream Restoration

Beginning in 2018, RES provided full delivery stream restoration services along Mardella Branch in Baltimore County, MD. This project is one of six that RES implemented under Maryland State Highway Administration’s Full Delivery Stream Restoration Services contract to help meet SHA’s total daily maximum load (TMDL) requirements.

The project was broken down into two distinct reaches (North and South) divided by Offutt Road and totaling 2,881 LF. This project was designed utilizing a Natural Channel Design (NCD) approach while also facilitating more frequent floodplain access during high-flow events. In addition to substantial nutrient pollution reduction, the Mardella Branch restoration generated co-benefits including greater floodplain reconnection, wetland generation, and habitat and biodiversity recruitment post-construction. RES’ responsibility included site selection and coordination with private landowners, design, permitting, construction, and long-term monitoring.

During construction RES utilized mulch and deckmat access roads to limit overall ground disturbance and over compaction of subsoils. Having been involved in the site development allowed for a high-use of site-generated materials; all of the trees that were removed for construction were utilized in the creation of stream structures and additional access paths, and the existing streambed material was utilized in the stream pool and riffle areas. Instream structures and features that were implemented included imbricated toe protection, log sills, log drops, toe wood, live lifts, riffle and pool combinations, and the creation of oxbow wetland within portions of the abandoned stream channel.

The Mardella Branch watershed continues to be rapidly developing with yearly increases in the overall impervious area upstream of this site; the implementation of the RES approach will result in the reduction of 392 pounds of phosphorus, 851 pounds of nitrogen, and 68 pounds of sediment per year for this watershed.

This project required close coordination with several interested project participants and entities including the property owners, SHA, Baltimore County, Maryland Department of the Environment (MDE), the US Army Corps of Engineers (USACE), and various subcontractors and suppliers. As this stream has a Use III designation and closure period from October 1 through April 30, RES’ coordination and logistics among the project participants allowed for successful and on-time delivery.

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