The Relationships Among Culvert Characteristics and Culvert Sedimentation

The purpose of this study was to investigate the relationships among various culvert characteristics and their effect on sediment deposition in culverts. The analysis included obtaining site specific field data, watershed modeling, culvert modeling, and data interpretation.

Field data was acquired for 39 culvert locations scattered across the City of Knoxville. The locations were selected based on previous maintenance records and a good distribution of characteristics subject to evaluation. The data collected included slopes, culvert material types, culvert sizes, culvert lengths, headwater depths, upstream channel conditions and downstream channel conditions. Obtaining this information required a detailed site inspection including surveying, culvert and sediment measuring, and a visual inspection and site evalution. In addition, hydrologic and hydraulic models were also used to evaluate culvert site characteristics at study locations. The information from field investigation as well as model output was evaluated by graphical depictions and statistical comparisons. Also, data were evaluated for culvert locations that had a minimal amount of sediment build up versus those culverts with a significant sediment buildup.

Findings revealed that six of the characteristics evaluated showed some relationship with culvert sedimentation. Culvert characteristics were divided into three tiers of influence. Each tier was analyzed and assigned a numerical value in order to develop a maintenance index. This index is proposed for use in evaluating whether a culvert, existing or proposed, may be prone to sediment deposition problems. Recommended research includes the relationship between debris and culvert sedimentation, the effect of the sediment yield from a watershed on culvert sedimentation, the relationship between the seasonal rainfall effects and culvert sedimentation, and additional statistical analysis on the data compiled within this study.