Imperfect FunGal

If we think of riparian areas, it’s usually in connection with a drainage ditch, or that scruffy area next to the water that I need to mow down because it’s blocking my view of the water. That’s even if we’ve ever heard the word riparian. Full transparency, this time last year, I googled it because it was in my Master Naturalist textbook, talking about an area where birds lived.

Riparian areas are the land areas between the water and the upland area from that water. To make it a little more muddy, the area doesn’t even really have to have water. A dry creek can still have a riparian zone. I will be writing another article diving into the details of these zones, but this should be enough context to discuss the plants and how they affect our urban areas.

Quick Riparian Zone Facts

• Riparian Zones account for about 1% of the total land area in Texas
• They provide amazing habitat for plants, animals, insects, and funga/bacteria
• Water, soil, and vegetation work together to create a healthy riparian area
• A healthy zone can slow floodwaters, as well as create and destroy land surrounding bodies of water

Looking at a riparian area there are multiple sub-sections (bank, mid-level, and uplands) that piece together to form a whole picture of the riparian zone. This zone then forms a protection layer from floodwaters and pollution that otherwise could easily impact our urban areas.  

What Makes Up A Riparian Zone

The bank is the area right next to the water (or where the water could be). This area has established soil, but it also gains and loses soil and sediment as water moves through the area.  

You should see two consistent types of banks next to your body of water:

• Cut Bank – this is the area where soil and sediment are being eroded from when water flows through
• Point Bar – this is the area where soil and sediment are deposited as water flows through

The bank and the channel make up the flood plain (natural areas where water expands to when flooding occurs). You might also hear this called the riparian sponge. The plants living in the sponge include wetland plants (need lots of water) and upland plants (need less water).  

When this area is unhealthy (area is manicured/mown, lots of barren areas present) the riparian sponge cannot hold the water in place. Water will continue to quickly flow through, causing erosion and carrying debris and pollutants further downstream. When this area is healthy (lots of different kinds of plants, heavy coverage) the water slows down, and by the simple act of existing the plants will slow down water. The water can then be filtered through the plants’ roots or pool in place to be filtered through the stones that make up the aquifer entrances/recharge zones.

Are We Getting to the Part About the Plants?

When we think about gardening, we typically go buy some plants that we like, put them in the ground, add water and magic, we have a nice yard. That’s amazing, but riparian areas are constantly moving and changing because water is always bringing in and taking away soil and sediment. Because of this, riparian plants have had to evolve and work together to populate these special areas. The first plants will simply find a spot and start growing, these are followed by plants that form root mats that help plants stay put long enough to grow deeper roots, and finally this provides a base for plants with deeper roots to grow and stabilize the entire area. (we’ll go into more detail on this later)

The best news is that with time and effort, even severely damaged riparian areas can go from unhealthy to healthy, oftentimes just by us stopping whatever we were doing to damage the area. 

Just like making a recipe at home, you will need a unique blend of ingredients to make a healthy riparian area. We look for plants based on the following ingredients:

• Do they survive better in wet or dry conditions
• How stable is their root base, how likely are they going to stay in place
• How hardy are the plants (common enemies are flowing water, direct sun, high winds)

First, let’s talk about the water needs for plants that live in this area.  They can be classed as:

• OBL – Obligate Wetland plants – Mostly found in the wet areas
• FACW – Facultative Wetland Plants –  Usually found in wet areas
• FAC – Facultative Plants – Can be found in wet or non-wet areas – they aren’t picky
• FACU – Facultative Upland Plants – Usually found in non-wet areas
• UPL – Upland Plants – Mostly found in non-wet areas

Next, let’s talk stability. The easiest way to think of this is that you have a plant enter the area and it grabs onto any place it can, those roots break up a little of the soil to make room for larger plants that break up a little more of the soil, which then leads to big plants/trees that can now dig deep into the soil and hold large banks in place. The stability rankings are from SR1 – basically the plant has to grow onto a bare rock, to SR10 – has the same stability as an anchored rock. You need a mix of plants with a SR6-SR7 rating in order to have adequate bank stability (AKA the bank and channel are not eroding away every time water passes through).

Finally, these together are used to identify the plants in the riparian sponge and the order in which they need to exist in the area to make it productive. 

• Pioneers
  • They are the first ones in, they grab onto what they can and hope for the best. 
  • They grow quickly in areas of high sun and poor soil.  
• Colonizers
  • They are that second group that comes in to create the root mats. They are slower to grow than pioneers, but spread quickly. You will usually hear them in connection to 2 categories:
    • Early stage colonizers – low stability rating, but starting to form the necessary structure or skeleton for the area.
    • Late stage colonizers – mid-level stability ratings, they are starting to break up the soil so that larger more stable plants can grow.
• Stabilizers
  • The last ones to the party, but they mean to stay.
  • It takes them a long time to grow, but once they are established, they are difficult to move.

Type	Wetness Indicator Range	Stability Range
Pioneers	FAC, FACU, or UPL	SR5-8
Early Stage Colonizers	OBL, FACW, or FAC	SR3-5
Late Stage Colonizers	OBL or FACW	SR6-7
Stabilizers	Any	SR7-9

The trick of all of this is that, unlike a garden, you will not be successful if you plant all the things and hope. The soil will not be ready to support a stabilizer if the pioneers and colonizers have not done the work to break up the soil. Their roots simply will have a much harder time breaking through the soil on their own, and weather events, like a flood, could take them out prior to them being established. This would lead to more debris downstream in a body of fast-moving water. It’s also important to remember that pioneers are not just by the water and stabilizers are not just in the upland areas, this evolution of the soil is happening at all levels of the channel. At any given moment, you can have all plant types and stages growing together if you have a healthy riparian sponge.

The plants I’m showing are mainly for the Texas area, and based on plants that I have observed in the wild, these can change across ecosystems. For Texas I highly recommend the “Your Remarkable Riparian Field Guide.” It is one of the few resources that will show you both the wetness and stability indicators.

Common Pioneers:

Common Early Stage Colonizers:

Common Later Stage Colonizers:

Common Stabilizers:

Why Do I Care?

We’ve been through the plants, why they are important to the actual ecosystem, but not how this affects you day to day.

According to the Texas Water Development Board’s 2020 survey, a whopping 55% of water usage was for irrigation.  First off, ouch.  More importantly, that shows that we really love our yards here. Because of the harsh conditions in Texas (lots of sun, drought, hot) we also tend to use a lot of chemicals to keep those plants and yards green and kill the plants we don’t like  – chemicals that are not great for our waterways. 

When we water our lawns, or it rains, these chemicals leech from our yards and into the drains, creeks, and drainage ditches. This is commonly referred to as non-source pollution. We know that chemicals are entering the waterways, but we don’t have a specific origin point. These pollutants can affect plant and animal life in the waterways (fish kills, algae blooms, toxicity to animals drinking the water), and selfishly, they can also affect our ability to use the waterways for activities like swimming, fishing, and paddle boarding. Having a healthy riparian sponge means that plants can help to filter out those pollutants making the waterways safer for everyone involved.  

From another perspective, we are seeing major changes in weather events, which mainly translates to microburst storms, aka storms that dump more water in a shorter period of time than we have previously seen.  When we look at some of the most recent floods, our waterways have handled larger overall rainfall (The July 4th 2025 flood crested on that day at only the 3rd highest crest in history – even though it was far deadlier than previous floods^*), but the velocity of the water was new.  

The major difference with more recent floods is that we have manicured riparian areas so that defenses like downed trees and stable riparian plants are no longer present.  In exchange we now have clear paths to the waterways and tree-free canoeing. Without these barriers, the waters arrive more quickly and move through at a faster rate. Faster water means the water takes on more erosion/debris. Quickly moving water can do a lot of damage, but quickly moving water with a lot of debris can turn a bad situation worse.  

The good news is that by letting some of these areas grow back (naturally) and leaving some of the barriers in place (like downed trees) we can have built in flood protection that not only slows down the water to give people additional minutes when seconds count, but can also trap the water in areas so that it can be filtered by the plants, or make it’s way into the aquifers versus passing over them.  

DIY Science

If you are like me, experiments are the spice of life. I would suggest a few DIY projects that can help you see the importance of the riparian sponge from your own backyard.

For Adults

Build a rain garden! This allows you to see the changes in how water pools around your yard and decreases overall runoff. 

1. You need to call 811 (do not skip this step, really) they will come out and mark your yard so that you don’t accidently damage your underground infrastructure – nothing ruins arts and crafts time like having to repair underground lines. This has never taken more than a couple of days for them to come out and mark.
2. While you’re waiting, read though this grow green guide on building rain gardens. I have read a lot of these, this is the one that takes you step by step through the process. If you hate reading, you can also watch the video. Get any materials you will need for your project.
3. Follow the guide  and build your new garden taking note of step 2 when you are digging the hole and testing how quickly water absorbs into the ground. Pro Tip:  Make sure to buy native plants for your garden to get the best bang for your buck!
4. Once it rains, pat yourself on the back for creating a tool that looks amazing and helps your neighborhood.  

For Kids

This is a quick experiment that can be done with items already in your house or in your yard. This experiment will help you to understand:

• How an unhealthy system acts
• How making small changes can still help to improve the system
• How a healthy system acts
• What happens when the system is at capacity (aka too much rain)

What You’ll Need:

• A cookie sheet or pan that will hold water
• Leaves, branches, rocks, sticks from your yard
• A sponge that you feel ok cutting up (this is going to sub in for our plants)
• A book or object that you can rest the top of the cookie sheet on to create an incline (if you’re like me, waterproof is probably best)
• Water
• Stopwatch (optional)

How To Do It

1. Send the kids outside to gather the leaves, branches, rocks and twigs from the yard. While they are doing this, cut the sponge into ½”X½” cubes.
2. Once the kids have gathered up their materials, take all your materials outside. (since you’re playing with water, outside will likely make less of a mess) Place the cookie sheet on your object to create an incline.  
3. This step shows how an unhealthy riparian zone would behave.
   1. Pour some water down the cookie sheet.  
   2. Take note of how long it takes for the water to slide down the cookie sheet to the bottom. (it should be pretty fast)
4. This step shows how a recovering riparian zone would act.
   1. Add your found materials from the yard to the cookie sheet. These act as fallen trees, natural boulders, and debris in your riparian zone.
   2. Pour water down the sheet again.
   3. Take note of how just having additional rocks and debris can help to slow down the water. (It’ll still be pretty fast, but it’s adding obstacles for the water and decreasing the water’s overall speed).
5. This step shows how a healthy riparian zone would act.
   1. Leave all of your found materials in the cookie sheet but add in the dry sponge – the sponge will act as the plants, taking in water through their roots.
   2. Pour the water down the sheet again.
   3. Take note of how long it takes. Repeat this step until the sponges are full of water. You will see that as the sponge’s ability to take on more water increases, it will continue to decrease the overall velocity, just like the plants. This is also a good way to see how once a system has reached capacity (aka the sponges are full of water) the water no longer has a place to go and “flooding” will happen.

Want To Get Involved?

1. Texas Stream Team is always looking for citizen volunteers to help monitor water quality and riparian zones – training is free and held monthly at the Meadows Center in San Marcos.  (Calendar)
2. Plant native and cut out the pesticides and fertilizers. Plants that are native to the area will grow without these helpers and there are many natural solutions to help with pests like mosquitos (dragonflies, mosquito minnows, citronella) and things eating your garden (BT – though this may also harm your pollinators).  The Native Plant Society of Texas offers guides for all areas of Texas to help you find plants that will work best in your area. 
3. Educate yourself – Organizations are always looking for people to get involved, or even just to listen to all of the crazy things they are passionate about when it comes to water and riparian areas. A lot of these are available online or in person, we aren’t scary, but if you’re nervous, bring a friend along!
   1. Grow Green Guides (available in English and Spanish) or look on YouTube for their Videos.
   2. Stream Team
   3. Hot Science – Cool Talks
   4. Waterloo Greenway – Fun activities for kids and adults
   5. Save Barton Creek Association
   6. San Marcos River Foundation – SMRF
   7. CER Lectures and Hornsby Bend
   8. Texas Master Naturalists

^* This tweet was verified by the Austin Water Center for Environmental Research (CER). In later days as the flooding continued, the crest did reach the top spot due to water flowing in from upriver locations, however the loss of life was due to the initial surge.