Flood recovery – walk don’t run.
The flood has passed and you’re shifting from emergency response to recovery but don’t rush into action. There’s a lot to learn from the flood that can inform recovery options and possibly prevent or minimise similar damage in the future.
Here’s three suggestions:
Post flood assessments
Before rushing in to clean up fences, pull out debris jams or “rock those banks”, waterway managers should spend as much time as possible (available) to learn from the flood. This includes identifying and documenting:
positive aspects resulting from the flood. Not everything flood-related is negative, for example:
Did any reaches ‘survive’ the flood with minimal or no damage? What was different about them that made them more resistant? What lessons can be learned that could be applied to other reaches?
Did any project sites ‘survive’ the flood? What was different about them? How did they compare to non-project sites?
Were there any projects or programs that decreased the impact of the flood e.g. less damage, reduced flood extent?
Has the flood created any management opportunities e.g. opening up reaches to enable woody weed control?
Has the flood improved diversity e.g. scouring out sediment, inputting timber?
negative aspects resulting from the flood. Don’t just document the damage, learn from it. For example:
Were there particular design aspects that may have caused of some projects or programs to fail?
Were there any projects or programs that increased the impact of the flood?
Post flood remediation
Connectivity between flood waters and the floodplain can be impacted by:
water regulation and extraction (which reduces the volume of water available to the floodplain)
channel incision or modification (which reduces the ability of a stream to overtop its banks)
actions taken to protect property from flooding, mostly by building levees
infrastructure which cross and disconnect floodplains e.g. roads.
Rather than just concentrating on remediating flood damage at the site scale, an opportunity exists for waterway managers to develop broader works programs (such as re-engaging the floodplain or reinstating floodplain wetlands) to assist in reducing flood peaks and velocities and managing flood extents.
Future flood forecasting
Once you have a program of works in place, you could document how they are likely to perform if there were another flood event in the short, medium or long-term. This could assist in increasing the robustness of your proposed works whilst also documenting a set of assumptions for future evaluation.
These documented assumptions could be ‘blind tested’ against the most recent flood. Using pre-flood aerial photography, map the likely flood impact zones (with reasoning documented) and compare these zones against post-flood photos. Did the assumptions hold true?
