Historic flood levels are an important input to flood studies to help with hydraulic model calibration and to improve the precision of flood frequency analysis. A collection of old bridge plans from Victorian Railways (Victoria, Australia) is available that includes information on flood levels from some of the largest floods from the late 19th and early 20th Century. From newspaper reports, we know these were big floods, but information on levels is hard to find which means the observations noted on these plans are a valuable resource.
A link to a PDF file with 409 plans is here:
I’ve pulled out some examples in the following figures.
Mitchell River, 1870 flood level at Bairnsdale
Figure 1: Mitchell River at Bairnsdale, 1870 flood level (link to plan)
Nicholson River, 1893 flood level at the Nicholson Bridge
The 1893 flood was a very significant event in this area, resulting in a change in course in the nearby Tambo River which isolated a wharf which was important for river traffic at the time (Erskine et al., 1990).
Figure 2: Nicholson River at Bairnsdale, 1983 flood level (link to plan)
I’ve looked through all the plans and found flood levels for about 15 waterways as noted in the following table. Not all of these will be useful but there are a few gems such as the 1934 flood levels in Orbost which include velocity estimates.
| Waterway | Location | Page number in PDF | Comment |
|---|---|---|---|
| Back Ck | Taradale | 381 | “Max” flood level |
| Goulburn River | Toolamba | 400 | 1870 flood |
| Jacksons Ck | Sunbury | 361 | 1916 flood |
| Maribrynong River | 168 | ‘Adopted’ flood level | |
| Mitchell River | Bairnsdale | 178 | 1870 flood |
| Moonee Ponds Ck | Jacana | 221 | ‘Adopted’ flood level |
| Moorabool River | 223 | ||
| MurrayRiver | Albury | 265 | Flood sometime prior to 1882 |
| Murray River | Tocumwal | 388 | Flood prior to 1892 |
| Nicholson River | Nicholson | 275 | 1893 flood |
| Saltwater River (Maribyrnong) |
Footscray | 334 | 1906 flood |
| Snowy River | Orbost | 301 | 1934 flood |
| Stoney Ck | 351 | ||
| Tambo River | Bruthen | 371 | |
| Thomson River | Sale | 317 | Flood prior to Nov 1874 |
| Yarra River | Richmond | 310 | 1863 flood |
| Woady Yallock Ck | 405 | 1909 flood | |
| Wombat Ck | 407 |
Good one Tony, out of interest, what datum were those plans in? We have often had to track down conversions for some of those old plans.
There is also a collection of Keel and Drape plans in northern Victoria which include some useful feature survey from the early 1900s, and sometimes some flood marks.
Datums are tricky and won’t be consistent between plans. The Australian Height Datum wasn’t established until 1971 so levels prior to this have to be adjusted to AHD. These adjustments have been established in some areas and will likely be known by local surveyors. Alternatively it might be possible to survey some point on a bridge that has a level indicated on an old plan and then work out the conversion.