With heavy rains raging across central Missouri, the Big Muddy’s old-fashioned flood control system is showing its age. Floodwaters this summer overwhelmed reservoirs north of Kansas City and are surging through central Missouri. After assessing lessons learned from the recent deluge, lawmakers are considering a new approach to flood management in Missouri. River engineer Gerald E. Galloway, for example, says it’s time for a new flood management plan in Missouri.
Community-based flood management
In order to prepare for a flood, communities in flood-prone areas should develop a disaster preparedness plan. These plans identify the resources needed to respond to a flood, such as temporary levees, sand bags, clay, food, and clean-up kits. Flood response efforts also include providing search and rescue resources. Developing a flood preparedness plan can help communities avoid losing lives and property during a flooding event.
A flood mitigation system can be effective in short-duration, low-velocity floods, and a combination of both. This type of flood mitigation strategy also requires enforcement and maintenance. In Appendix II, floodproofing limitations are clarified. The flood mitigation decision tree shown in the Decision Tree Example illustrates how to make this type of decision. The CRS framework also allows for multi-period comparisons to determine whether community-based flood management practices improve flood insurance premium rates.
A stream restoration project will improve flood resilience by improving stream habitats and ecosystems. In addition, it will reduce downstream damage caused by floods. By restoring floodplain habitats, streams can protect people and property. Restored streams can also provide important societal services, including enhancing spatial connectivity of river habitats. So, community-based flood management projects can be a useful tool for Missouri’s storm-prone regions.
The recent spate of failures along the Midwest’s levees has raised questions about the durability of flood-control systems. Conservation groups have criticized the scattershot approach to flood-control and have argued for a more comprehensive approach. These failures have also exposed the risks of future disasters. In addition, some states such as Nebraska and Iowa are rebuilding levees that have failed in the past. These failures also have resulted in the displacement of entire communities and homes from floodplains.
However, in the case of Missouri, it is not enough to just rely on levees to mitigate flooding. The state of Missouri is attempting to convince the Army Corps of Engineers to reconsider its current levee system, in an effort to prevent problems similar to those that caused the flood of 2019. By working together with the states of Kansas, Nebraska, and Iowa, state officials hope to prevent the same mistakes that caused the recent disaster. In addition, a regional approach can reap benefits from targeted investment.
The Corps of Engineers and the National Flood Insurance Program could learn from the painful experience and mandate mitigation alternatives in levee repair projects. For example, recipients of repeated levee repair funding could be required to consider other mitigation measures, such as buying out homes. Further, local jurisdictions should recognize that there is a residual risk associated with living behind levees and steer new development toward flood-safe areas.
The recent flooding events in the Mississippi and Missouri basins caused over $20 billion in damages. This flood event was twice as long as the 1993 flood, with some locations on the Missouri River and Mississippi River flooded for nearly 100 days. The state of Missouri is expecting more frequent and more intense rain events in the future, making new flood protection strategies necessary. The Missouri Department of Conservation is utilizing LiDAR mapping and its associated data to create a Flood Management Approach.
The new LiDAR-based technology allows for a more accurate mapping of flooding events. LiDAR mapping can be used to detect flood water a few days in advance and help forecast and manage water resources in an area. A recent example of the use of LiDAR-mapped floods is shown below. The flood water levels in St. Louis were six meters higher than flood stage. The 16-m high St. Louis Floodwall held out the flood with just 0.6 m of extra height. This mapping tool was developed by NASA and is available for use in flood disaster management efforts.
The proposed method employs a hydrogeomorphic index that combines the distance to the nearest drainage and two normalized geomorphic features. These are the primary data used in flood hazard mapping. This index relies on a calibration procedure that varies the weights of the geomorphic features in a region and determines which one is more appropriate for flood hazard mapping. The model is trained using a variety of different return periods of water levels. The resulting map will have different thresholds for each water level return period.
Conservation of floodplain vegetation communities
In the United States and Europe, large tracts of floodplain have been restored. In Missouri, the U.S. Fish and Wildlife Service and state and federal agencies have acquired 35,000 hectares of floodplain lands along the Missouri and Mississippi rivers. In addition, additional lands are managed under various conservation easements. These floodplain properties have largely been converted from agricultural production to natural land cover and are managed for conservation.
Restoring the wetlands provides an opportunity to assess changes in hydrology and plant community composition. Restoration projects aim to increase the hydrological conditions that support target plant species. In addition, they aim to study the response of plant species to restoration projects in terms of their functional traits. Until now, only a few studies have been conducted on these restoration efforts in Missouri. But the findings are promising for both conservation and management of floodplain ecosystems.
In a follow-up survey to the workshop, twenty-one floodplain managers participated. Seven of them are associated with properties on the MMR and the LMOR. Four more are associated with properties on the UMR and the Illinois River. In addition, 16 other resource managers expressed interest in attending but had time conflicts or travel restrictions. However, this was not possible, and a larger group of floodplain managers may have attended.
Economic impact of road closures
Using the Missouri River as an example, the United States Army Corp of Engineers develops plans for upstream water release, which can increase flooding. In 2011, a major river crossing along the Missouri River was closed, causing massive impacts. Fortunately, the Missouri DOT managed to issue emergency contracts, conduct repairs, and reopen the river crossing before another flood. However, after the 2011 flood, a major river crossing in Missouri was closed again.
The National Oceanic and Atmospheric Administration (NOAA) and National Weather Service (NWS) provided flood gauge data and hydrographs that could be used to model the flow of water. This data could include details about downstream bridges and road dams. Supervisors had access to these tools through mobile devices, and they could better determine when water would be released from upstream dams and when to position heavy equipment to keep the roads open.
In the case of Missouri, over 470 miles of roads were closed and many were underwater for several weeks. In addition, one hundred and eighty levee breaches were not repaired until a year after the flood, and several roads were under water during that interim period. In order to plan for these impacts, the Missouri DOT was required to understand how to assess damage and work within the timeline set by other agencies. This was a critical task because flood events had stretched the District’s budget.
Efforts by State DOT to reduce flood risk
Across the United States, the number of flood-related disasters is increasing. In the last decade alone, floods have caused more than $845 billion in damages to homes, businesses, and critical infrastructure. The cost of adapting to increasingly frequent storms will only increase, so taking action now can reduce the impacts of floods in the future. In Massachusetts, the State DOT has taken steps to address this problem and improve flood-safe roads and bridges.
The first step to addressing the problem was to understand the causes of flooding. State and local officials in Minnesota and Washington state took advantage of a grant from the Environmental Protection Agency to research flooding and develop flood mitigation policies. They assessed flooding impacts on their transportation assets and identified the worst-affected areas. By taking this information into account, Minnesota officials were able to maximize the effectiveness of their limited funds.
Using this information, the CMAP should design new projects to address potential flood risks. It should also conduct a regional climate vulnerability assessment of transportation assets to inform long-range planning and programming. It should also develop a regional pavement flooding reporting system. Once these measures are implemented, they will be better prepared to respond to floods when they occur. This study is an essential step to ensuring a safe and resilient transportation network in the future.