Low-Water Crossings: An Overview of Designs Implemented along Rural, Low-Volume Roads

Abstract

Replacement of many old and aging bridges, culverts, and low-water crossings on rural low-volume roads is an increasing concern throughout the United States. The economic burden for many local bodies can be huge if these structures are to be replaced by a bridge or culvert. A low-water crossing (LWC) is a feasible and efficient road-stream crossing structure that can be used on these roads as an economical alternative to culverts and bridges. Three types of commonly used LWCs; unvented fords, vented fords and low-water bridges; their selection criteria, environmental considerations, design process, materials selection, signage and permitting requirements are included in this paper. Some of the issues with the existing LWCs are the safety in the crossing and effects on aquatic organism passage and surrounding environment. Through proper design, construction, and installation of proper signage, the functionality and reliability of LWCs can be improved. The study provides engineers and other practitioners in the United States and elsewhere with a proper set of information and design procedures for using LWCs.

Role of transportation infrastructures on the alteration of hillslope and fluvial geomorphology

“…Identifying any river without a single causeway will be a challenging job. There must be a presence of any form of causeway either ‘ low-water crossing ’, a structure implemented on a road with average daily traffic of fewer than 25 vehicles, vented or unvented (<6 inches of flow depth) and water run over the roadway at the high flow of stream (Gautam and Bhattarai, 2018; Ring, 1987) or a ‘ road-stream crossing ’, which is any bridge or culvert passing over a creek, river, stream or formed channel (Melbourne Water, 2011). Bridges are defined legally as structures with a centreline span of 6 m or more, whereas, the culvert is a crossing structure with 6 m or less in centreline span width between extreme ends of openings in different shapes (Federal Highway Administration (FHWA), 2012; Indian Roads Congress (IRC), 2004; National Bridge Inspection Standards (NBIS), 2006).…”

Qualitative investigations into floodways under extreme flood loading

“…Greene et al (2020b) undertook a comprehensive Australian-based industry survey in 2020 to investigate the experiences of asset owners concerning extreme flood events and the prevalence of impact-related failures, thus providing a qualitative dataset in relation to practical experiences post extreme flood events. In the international context, two other floodway specific surveys were undertaken by Lohnes et al (2001) and Gautam and Bhattarai (2018). The survey conducted by Lohnes et al (2001) was in response to developing a design guideline with respondents from various municipals within the United States.…”

“…The survey outcomes suggested a strong dependence on in‐house design standards, a preference towards vented floodways, as well as providing a summary of floodway applications. The survey by Gautam and Bhattarai (2018) summarized the consensus of floodway uses as being within rural settings, on roads with low average daily traffic volumes, to provide an economical alternative to bridges and culverts, and that the overtopping duration should be based on utilization category and limited to less than 5% per year.…”

Embracing Uncertainty: Using Probabilistic Weather Forecasts to Make Ensemble Hydraulic Predictions at Remote Low-Water Crossings

“…In this work we focus on low-water crossings (LWXs). These structures are at grade, or slightly raised, with respect to a streambed (Gautam and Bhattarai 2018). As such, LWXs are designed to be overtopped by high flows and closed to traffic (Carstens and Woo 1984).…”

“…An LWX is an appropriate structure for roads with average daily traffic of less than 25 vehicles (Gautam and Bhattarai 2018;Rossmiller et al 1983). This requirement results in LWXs being implemented in remote locations.…”