Understanding and Managing Mobile Rivers in Agricultural Lands: Examples from Indiana, U.S.a.

In 2008 a series of floods caused extensive damages (road sections, bridges, culverts damaged or destroyed) across the state of Indiana, and prompted the need for a more complete understanding of the dynamics of Indiana’s rivers and streams. In an effort to reduce the continuing risk to flood damage, a Fluvial Erosion Hazard (FEH) Mitigation Program was initiated. The initial products from the program were regional hydraulic relationships (regional curves) for Indiana streams that provided an understanding of the variability in stream types across the state, and an assessment of the lateral mobility of selected Indiana streams. The mobility assessment measured channel-migration rates at 970 meander bends on the 38 largest streams in Indiana. The analysis indicated that 65% of the meanders were moving at <1 ft/yr, and 75% of the meanders were moving at <10 ft/yr.  While the initial focus of the FEH program had been on infrastructure, the loss of farmland due to channel migration has also emerged as a serious concern. Whereas infrastructure risk can be addressed with a variety of methods, ranging from avoidance to protection, the miles of mobile rivers that flow through farmland will require an understanding of why certain streams are so laterally mobile. In this presentation we will describe the preliminary findings of an investigation into what drives the increased channel migration of some Indiana streams, and review a case study from the investigation.