Related Experiment Video
Updated: Aug 2, 2026
12:44
Watershed Planning within a Quantitative Scenario Analysis Framework
Published on: July 24, 2016
Testing the basic assumption of the hydrogeomorphic approach to assessing wetland functions
1Washington State Department of Ecology, Olympia 98504, USA.
Environmental Management
|May 4, 2001
Summary
The hydrogeomorphic (HGM) approach assumes least-altered wetlands are best, but this study found this assumption invalid in western Washington. Unaltered wetlands showed varied function levels, challenging HGM
Area of Science:
- Environmental Science
- Ecology
- Hydrology
Background:
- The hydrogeomorphic (HGM) approach uses reference standard sites to develop rapid wetland function assessment methods.
- A key HGM step is selecting least-altered wetlands as reference standards to compare against other wetlands.
- The core HGM assumption is that least-impacted wetlands exhibit the highest sustainable performance for all functions.
Purpose of the Study:
- To test the validity of the HGM approach's core assumption in western Washington wetlands.
- To determine if least-altered wetlands consistently represent "characteristic" and "sustainable" function levels.
Main Methods:
- Studied 44 wetlands across four hydrogeomorphic subclasses in western Washington.
- Expert teams assessed human alterations (water regime, soils, vegetation, buffers, basin) on a 1-5 scale.
- Wetland function performance was rated on a 1-7 scale for 15 functions.
Main Results:
- Least-altered wetlands did not consistently display "characteristic" or "sustainable" function levels.
- Unaltered wetlands exhibited a wide range of performance ratings across all assessed functions.
- The HGM assumption that least-altered wetlands represent a distinct, higher performance standard was not supported.
Conclusions:
- The fundamental assumption of the HGM approach is not applicable to western Washington wetlands.
- Using least-altered wetlands as a sole benchmark for "characteristic" and "sustainable" function may be inappropriate in this region.
- The HGM approach's utility for assessing wetland ecological integrity in western Washington is questionable based on these findings.
Related Concept Videos
01:14Testing Water Quality
When the quality of water for concrete preparation is uncertain, its impact on the setting time of cement and compressive strength of mortar is assessed by comparison with de-ionized or distilled water benchmarks. American Society for Testing and Materials (ASTM) C1602 requires the setting times to be within 90 minutes of the control, British Standard (BS) 3146:1980 allows a 30-minute variance in the initial setting, while British Standards European Norm (BS EN) 1008 specifies initial setting...
01:30Typical Model Studies
Fluid mechanics model studies often utilize scaled-down systems to predict fluid behavior in full-scale environments, such as river flows, dam spillways, and structures interacting with open surfaces. Maintaining Froude number similarity in river models is crucial, as it replicates surface flow features like wave patterns and velocities.
01:21Design Example: Creating a Hydraulic Model of a Dam Spillway
Scaled hydraulic models of dam spillways provide a practical way to replicate and study the intricate flow dynamics of these structures. Often built to a 1:15 ratio, these models allow for observing critical water behavior, such as velocity distribution, flow patterns, and energy dissipation.
01:17Design Example: Analyzing Capacity Contours for Flood Risk Assessment
Flood risk assessment involves careful planning and analysis to ensure the safety of communities near water retention structures. Capacity contours are a vital tool in this process, as they illustrate the potential spread of water at specific levels in a given area. In the context of building a bund across a small valley, these contours play a critical role in evaluating the safety of nearby residential areas.In this example, the bund is intended to store stormwater in the valley. The engineers...
01:22Net Change Theorem
The Net Change Theorem is a fundamental principle in calculus that establishes a direct relationship between a function’s rate of change and its accumulated change over an interval. Mathematically, it states that the definite integral of a function's derivative over a given interval [a,b] yields the net change in the original function:This theorem has significant applications in various real-world scenarios, including physics, economics, and engineering. A particularly useful application is in...
01:30Microbial Wastewater Treatment
Microbial communities in aquatic ecosystems play a key role in the natural breakdown of contaminants introduced through domestic and industrial effluents. Acting as biological catalysts, these microbes change and mineralize a wide range of organic and inorganic pollutants under different redox conditions.In oxygen-rich surface waters, aerobic heterotrophs lead organic matter breakdown, using oxygen as the terminal electron acceptor to efficiently oxidize substrates to carbon dioxide and water.