District Department of Transportation
- Stream & Watershed Evaluation
- Geomorphic Assessment
- Hydrology & Hydraulic Analysis
- Stream Restoration Design
The District Department of Transportation (DDOT), in cooperation with the National Park Service (NPS), proposed to improve the overall condition and connectivity of the deteriorating Rock Creek Park multi-use trail system and design of a pedestrian bridge alongside of existing vehicular Beach Drive Bridge, in order to enhance visitor use and experience within Rock Creek Park. The design, when constructed, will result in:
- Improved visitor safety and experience and protection of park resources;
- improved access to the Rock Creek Park multi-use trail system from other pedestrian and bicycle facilities, as well as the surrounding neighborhoods; and
- more effective drainage and erosion control, thereby reducing trail maintenance.
An Environmental Statement / Finding of No Significant Impact, and a 30% design for the project were completed in 2014 (DDOT, 2013 and DDOT, 2014). The 30% design (DDOT, 2013) identified locations where the stream bank of Rock Creek should be stabilized in order to protect the improved trail. This report included data collected to evaluate the condition of two bank stabilization locations identified in the 30% design, located adjacent to the Smithsonian National Zoological Park.
In spring of 2016, the reach of Rock Creek that included both bank stabilization locations were examined and evaluated by CRI to assess the current creek conditions. CRI’s staff led the field work and analysis associated with the geomorphic assessment of 750 linear feet of Rock Creek. The project included survey of channel geometry and planform, analysis of bank erosion, identification of sources of channel instability, documentation of riparian vegetation, and development of a restoration concept. CRI prepared a stream assessment and concept report, which documented the methods, analysis and results of the geomorphic assessment.
CRI provided stream restoration design services for the Rock Creek Park Trail project. The key stream restoration design objective was to create stable banks with improved habitat, ecological function, and aesthetics, as well as to result in neutral or positive impacts on downstream areas. CRI developed a stream restoration design (30%, 65%, 100% and PS&E) to achieve the design objectives. CRI applied stream restoration design principles to stream banks in Rock Creek based upon the availability of adjacent land (including proximity to structures and buildings), and other relevant factors. CRI clearly identified the extent of adjacent land necessary to achieve the design objectives of a stable stream channel, and channel work on adjacent NPS property.
CRI revised the hydrology model provided by others for use in computing additional smaller storm events required for the stream design. CRI performed a flood recurrence analysis using data from the USGS gaging station at Sherrill Drive. This information was used to perform a hydraulic analysis of each bank stabilization area, including the structural stability based on scour calculations, conveyance capacity, and other relevant measurements.
CRI evaluated the amount of land available for the stream bank restoration so that the most environmentally and hydraulically sound stabilization methods were implemented. In areas where there is not enough land to do something more natural, bioengineering and imbricated boulder wall with vegetated slopes in addition to traditional stabilization approaches (e.g., floodwalls) were considered in coordination with DDOT, District Department of Energy and Environment (DOEE), NPS, and other stakeholders. CRI presented the staged review plans to DDOT, DOEE, and NPS staff and the stakeholder group. CRI revised the stream plans based on the recommendations of the stakeholder group. CRI also attended a meeting to help answer any questions regarding the bank stabilization from the general public. CRI assisted in preparing presentation materials to convey the nature of the bank stabilization work to the public and attended one stream walk to highlight key design elements and constraints in the field to stakeholders
CRI designed the erosion and sediment control plans for the stream restoration and pedestrian bridge installation. The erosion and sediment control met the requirements in the 2017 DOEE’s Erosion and Sediment Control Manual. The plans included phased work at three work areas along Rock Creek with sandbag diversions to dewater the work area located in the creek.
In January 2019 an undermined tree fell into Rock Creek along with a portion of the streambank exposing the combined storm and sanitary sewer at the site of the proposed bank treatment. CRI completed a Rock Creek Emergency Bank Repair Memo and Plan to temporarily restore the bank with riprap armoring until the permanent bank stabilization can be installed.