Most counties have bridges that are no longer adequate, and are faced with large capital expenditure for replacement structures of the same size. In this regard, low water stream crossings (LWSCs) can provide an acceptable, low cost alternative to bridges and culverts on low volume and reduced maintenance level roads. In addition to providing a low cost option for stream crossings, LWSCs have been designed to have the additional benefit of streambed stabilization. Considerable information on the current status of LWSCs in Iowa, long with insight of needs for design assistance, was gained from a survey of county engineers that was conducted as part of this research (Appendix A). Copies of responses and analysis are included in Appendix B. This document provides guidelines for the design of LWSCs. There are three common types of LWSCs: unvented ford, vented ford with pipes, and low water bridges. Selection among these depends on stream geometry, discharge, importance of road, and budget availability. To minimize exposure to tort liability, local agencies using low water stream crossings should consider adopting reasonable selection and design criteria and certainly provide adequate warning of these structures to road users. The design recommendations included in this report for LWSCs provide guidelines and suggestions for local agency reference. Several design examples of design calculations are included in Appendix E.
[1]
A K Motayed,et al.
DESIGN GUIDE: LOW WATER STREAM CROSSING
,
1982
.
[2]
Edwin Henry Gaylord,et al.
Structural Engineering Handbook
,
1968
.
[3]
L A Herr,et al.
Hydraulic charts for the selection of highway culverts
,
1977
.
[4]
B. Berg.
Shoreline erosion on selected artificial lakes in Iowa
,
1980
.
[5]
O. J. Larimer.
Drainage areas of Iowa streams
,
1957
.
[6]
R L Carstens,et al.
Liability and Traffic Control Considerations for Low Water Stream Crossings
,
1984
.
[7]
T J Wipf,et al.
INVESTIGATION OF TWO BRIDGE ALTERNATIVES FOR LOW VOLUME ROADS
,
1996
.
[8]
Robert J. Houghtalen,et al.
HYDRAULIC DESIGN OF HIGHWAY CULVERTS
,
1985
.
[9]
A K Motayed,et al.
DESIGN AND CONSTRUCTION OF LOW WATER STREAM CROSSINGS. FINAL REPORT
,
1982
.
[10]
Kem C. Kadavy,et al.
Rock Riprap for Grade Control
,
1996
.
[11]
Stanley L Ring,et al.
Design Manual for Low Water Stream Crossings
,
1983
.
[12]
Malcolm P Keown,et al.
Literature Survey and Preliminary Evaluation of Streambank Protection Methods
,
1977
.