Tier 1 Geomorphic Unit Protocol
The Tier 1 Geomorphic Unit Protocol is the preliminary assessment of a valley bottom. This protocol helps identify and categorize Tier 1 geomorphic units, or ‘building blocks’, of a riverscape, as well as define the lateral boundaries (i.e., margins) of the valley bottom.
The main purpose of this protocol is to inventory the resources that define a riverscape’s setting. This provides crucial insights into the natural and human-caused processes that shape a valley bottom. From this, a deeper understanding of channel form & function, geomorphic condition, and riparian health can be understood (Bennet et al. 2019). Furthermore, this protocol identifies sources of current or past human development or natural disturbances that influence or have altered the riverscape.
By understanding these processes, you can tailor more effective restoration actions that target key components of your riverscape and maximize ecological uplift. This includes setting realistic goals, managing expectations, and assessing potential risks in your riverscape (Bennet et al. 2019). Therefore, this protocol should be the first (and most important) step of the LTPBR planning phase.
The Tier 1 protocol should be completed before digitization of pre-project monitoring, design, or as-built implementation. Within QRiS, you can add this protocol to your project by right clicking on the Data Capture Events container, selecting the Low-Tech Process-Based Restoration option, and clicking on Add New Planning Container.
Protocol Summary
| Attribute | Value |
|---|---|
| Name | Tier 1 Geomorphic Unit Protocol |
| Status | Experimental Grade |
| Version | 1.0 |
| XML URL | https://github.com/Riverscapes/RiverscapesXML/blob/master/QRiS/protocols/tier_1_geounit_protocol.xml |
| Citation | Burgert et al. 2025. Tier 1 Geomorphic Unit Protocol. Prepared by Anabranch Solutions. |
| Author | Zach Burgert |
How to Use
The following step-by-step guide will show you how to map your riverscape using this protocol.
- Start by digitizing the channel lines within the valley bottom to map the location of the river network.
- Next, digitize all Tier 1 geomorphic units to identify the landforms that fundamentally shape the valley bottom.
- Then digitize the margins of the active channel(s), valley bottom, valley, and anthropogenic features to define their extents.
- Finally, determine which mapped margins are ‘confining’. These are the features that constrain a channel's form or function and set the physical limits of the riverscape.
Once those layers are digitized, you can calculate metrics to assess the valley bottom’s condition and its restoration potential. These include:
- Confining Margin Length: Total length of all confining margins.
- Confinement Ratio: Proportion of channel length confined by the valley bottom, valley, or anthropogenic margins.
- Constriction Ratio: Proportion of channel length constricted by the valley bottom, valley, or anthropogenic margins.
- Active Channel Ratio: The ratio of active channel area to valley bottom area.
- Active Floodplain Ratio: The ratio of active floodplain area to valley bottom area.
- Inactive Floodplain Ratio: The ratio of inactive floodplain area to valley bottom area.
Layers
| Attribute | Type | Metrics | Description |
|---|---|---|---|
| Active Channel Lines | Linestring | Confinement Ratio, Constriction Ratio | centerline of all natural and anthropogenic channel(s) within the valley bottom |
| Tier 1 Gemorphic Units | Polygon | Active Channel Ratio, Active Floodplain Ratio, Inactive Floodplain Ratio | landforms shaped and distinguished by vertical flood stage height |
| Margins | Linestring | NA | bounding extent of the channel, valley bottom, valley, or anthropogenic feature. |
| Confining Margins | Linestring | Confining Margin Length, Confinement Ratio, Constriction Ratio | abutment of the channel against the valley bottom, valley, or anthropogenic margin(s). Defined as the confining extent that constrains a channel’s form or function |
Layer Attributes
Active Channel Lines
| Channel Type | Description |
|---|---|
| Primary | longest continuous mainstem channel in the valley bottom. |
| Non-Primary | all other channel threads in the valley bottom. This includes anabranches, tributaries, braided channels, canals, or beaver canals that are separate from or connected to the primary channel. |
Tier 1 Geomorphic Units
| Geomorphic Unit Type | Description |
|---|---|
| Channel | Portion of valley bottom that is inundated by bankfull flow. Evidence of channel includes |
| Active Floodplain | Portion of valley bottom that is frequently flooded by the contemporary flood regime. Evidence of active floodplain can include active riparian vegetation, alluvial flood deposits, wood deposition, etc. |
| Inactive Floodplain | Portion of valley bottom that is not flooded or rarely flooded by the contemporary flood regime. Evidence of inactive floodplain can include relic riparian vegetation, upload vegetation encroachment, remnant alluvial and wood deposits, etc. |
| Terrace | Relic floodplain that is no longer flooded by the maximum contemporary flood regime. This includes floodplains that were once inundated by historic flood regimes before channel downcutting and resulting incision disconnected the channel from these floodplains and created new ones at lower elevations. |
| Alluvial Fan | fan-shaped sediment deposit formed where a channel exits a high-sloped area and enters a low-sloped area. These features consist of well-sorted alluvium that is deposited as the channel's velocity decreases. |
| Colluvial Fan | cone-shaped deposit of loose, poorly sorted sediment (colluvium) that forms at the base of a hillslope. It's created by unchanneled, gravity-driven processes like sheet wash or rainwash. |
| Moraine | ridge-like deposit of compact, unsorted sediment (glacial till) formed by a melting or retreating glacier. |
| Hillslope/Upland | steeply-sloped landforms outside of the valley margins. These features were never flooded or shaped by the historical flood regime and consist of colluvium or bedrock. |
Margins
| Tier 1 Type | Description |
|---|---|
| Channel Margin | outer extent of a channel, defined by its banks. |
| Valley Bottom Margin | outer extent of the valley bottom, defined by terraces or fans. |
| Valley Margin | outer extent of the valley, defined by hillslopes. |
| Marign Origin | Description |
|---|---|
| Anthropogenic | created or influenced by human activity |
| Natural | formed by riverscape processes |
| Natural and Anthropogenic | created, influenced, or formed by both riverscape processes and human activity. For example, a natural embankment with a wall built on top. |
| Tier 2 Type | Description |
|---|---|
| Embankment | artificial bank, wall, or mound, typically constructed with earthen materials such as soil, rock, or other aggregates. Its primary purpose is to provide an elevated platform for infrastructure to reduce flooding risk. |
| Fence | freestanding structure designed to enclose, delineate, or obstruct an area. It is typically constructed from a series of posts, wire, panels, or other components. |
| Hedgerow | barrier composed of a densely vegetated, layered planting of woody shrubs or trees. Traditionally used to limit soil erosion near the banks of rivers. |
| Constructed Levee | type of embankment specifically designed and engineered to contain, control, or divert the flow of a river and mitigate flooding. |
| Railroad | network or series of tracks used to transport trains. |
| Road | leveled pathway typically made of asphalt, concrete, or dirt designed to transport vehicles |
| Wall | upright structure typically made of concrete that serves to enclose, divide, or protect an area. |
Confining Margins
| Confinement Type | Description |
|---|---|
| Left | confining margin on river-left (looking downstream) bank |
| Right | confining margin on river-right (looking downstream) bank |
| Both | confining margin on both river banks |
Metric Attributes
| Metric | Description | Calculation |
|---|---|---|
| Confining Margin Length | sum of all confining margins digitized by the user | Sum(Confining Margin Lengths) |
| Confinement Ratio | ratio of confining margins classified as 'left' or 'right' normalized by the primary channel centerline | Sum (Length of Confining Margins [‘Right’ + ‘Left’]) / Length of Primary Channel |
| Constriction Ratio | ratio of confining margins classified as ‘both’ normalized by the primary channel centerline. | Sum (Length of Confining Margins [‘Both’]) / Length of Primary Channel*2 |
| Active Channel Ratio | proportion of the valley bottom that is inundated by bankfull flow. This includes channel polygons digitized in the Tier 1 Geomorphic Unit layer. | Sum (Channel Area) / Total Valley Bottom Area |
| Active Floodplain Ratio | proportion of the valley bottom that is flooded by the contemporary flood regime. This includes active floodplain polygons digitized in the Tier 1 Geomorphic Unit layer. | Sum (Active Floodplain Area) / Total Valley Bottom Area |
| Inactive Floodplain Ratio | proportion of the valley bottom that is not flooded by the contemporary flood regime. This includes inactive floodplain polygons digitized in the Tier 1 Geomorphic Unit layer. | Sum (Inactive Floodplain Area) / Total Valley Bottom Area |
References
Bennett, S.N., Wheaton, J.M., Bouwes, N., Jordan, C.E., Macfarlane, W.W., Maestas, J.D., Portugal, E. and Shahverdian, S.M., 2019. Chapter 3 – Planning for Low-Tech Process-Based Restoration. In: J.M. Wheaton, S.N. Bennett, N. Bouwes, J.D. Maestas and S.M. Shahverdian (Editors), Low-Tech Process-Based Restoration of Riverscapes: Design Manual. Utah State University Restoration Consortium, Logan, Utah. pp. 57.
Wheaton, J.M., Fryirs, K.A., Brierley, G., Bangen, S.G., Bouwes, N. and O'Brien, G., 2015. Geomorphic mapping and taxonomy of fluvial landforms. Geomorphology, 248, pp.273-295.