The following Questionnaire will assist you in determining what types of stewardship and recovery strategies relating to large woody material are the most applicable for your property.
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Large woody material (LWM) generally refers to dead trees, branches, limbs and logs. These may have been left on your streambanks by flood flows, or they may be the result of trees dying on your property. Large woody material can also come from high up on valley walls through mud or debris slides during or after heavy rains. Regardless of how the large woody material arrived on your property, the assessment and strategies to manage it are the same. While one goal of large woody material management is to reduce flood risks, you can also use large woody material to provide wildlife, vegetation and other environmental benefits to your property.
When evaluating large woody material on your property, you will need to decide if it poses a risk during floods or high flows. In general, large woody material provides many benefits to stream corridors and you only want to remove or relocate this material if you are sure it poses a risk. If you are unsure about if a piece of woody material poses a risk, please contact your local watershed coalition or a qualified stream restoration professional.
Where it does not pose a flood risk, large woody material is commonly referred to as ‘Good Wood.’ Having large woody material along streams and streambanks is a natural occurrence and Good Wood provides a variety of environmental and stream function benefits to your property. Floods naturally deposit Good Wood that can often be either left in place or relocated on-site.
Good Wood includes wood that is in the floodplain, along streambanks and within the channel. Having large woody material in the floodplain adds ‘floodplain roughness.’ Floodplain roughness refers to how quickly flood waters will flow over an area. By adding pieces of large woody material to the floodplain, flood waters can be slowed down. This is actually a goal of many stewardship and restoration projects because flood waters can be slowed down and wood can help capture smaller debris and sediment and help build up functional floodplain material. By slowing the water down, the large woody material is also creating more storage space for the flood waters. This does not mean that flood waters will stay in the area for long periods of time. Instead, this means that the flood waters will slow down and spread out in the floodplain, then slowly flow back into the stream as the flood recedes. This is in line with the natural progression of a flood event.
For a more in-depth and technical guide to evaluating and managing large woody material in stream corridors, please see this publication by the American Water Resources Association:
Good Wood will also often become wildlife habitat for birds, small mammals, insects and amphibians. It is an excellent source of carbon, the building block of life. As the wood decomposes, it adds organic matter (carbon) and nutrients back into the soils. Good Wood can also have benefits on how the stream moves and stores sediment, as well as habitat for aquatic organisms. Frequently the best strategy for managing Good Wood is to secure it (if necessary) and leave it in place. Depending on location, it may need to be anchored in place so it is not carried away by flood waters.
Using the Questionnaire on the following page, you will evaluate large woody material on your property. Evaluating large woody material can be difficult and it is easy to second guess yourself. When in doubt, contact your local watershed coalition or a qualified stream restoration professional for assistance evaluating the woody material. If you think the woody material may pose an immediate and imminent threat to roads, bridges or properties, contact your local (County or City) Office of Emergency Management. Contact information for these organizations can be found in the ‘Large Event Preparedness’ section of Chapter 1.