Selecting Between One-Dimensional and Two-Dimensional Hydrodynamic Models for Ecohydraulic Analysis

Abstract

14Aquatic habitat assessment and river restoration design require geospatially explicit maps of 15 hydraulic conditions. Diverse mechanistic ecohydraulic models compute spatially explicit depth 16and velocity results to evaluate habitat suitability spatially as a function of these abiotic 17conditions. This study compared depth and velocity results from two-dimensional (2D) and one-18 dimensional (1D) hydraulic models with algorithms that laterally discretize 1D velocity and 19 interpolate depth and velocity spatially based on the Laplacian heat mapping approach. These 20 'conveyance distributed' methods constitute 'best 1D modeling practice', and were compared to 21 2D results for the first time. The 1D and 2D models were applied to three morphologically 22 distinct reaches (leveed, meandering, and anastomosing) for three flows (base, bankfull, and 23 flood flows) of the partially regulated, gravel/cobble lower Yuba River in north-central California. 24The test metrics were the coefficient of determination (R 2 ) and the median absolute residual 25 ( ). These metrics quantified the incremental uncertainty 1D approximation incurs, results 26 which make explicit cost-benefit processes of model selection possible.

Kayak drifter surface velocity observation for 2D hydraulic model validation

“…To exemplify data resolution, within and beyond the wetted area at 24.92 m 3 /s, overall point density downstream of the Highway 20 Bridge was 59 and 554 points per 100 m 2 , respectively. As previously published in 10 journal articles (e.g., Gibson & Pasternack, ; Gonzalez & Pasternack, ; Wyrick & Pasternack, ), SRH‐2D (v. 2.1) was used to simulate meter‐scale, nonvegetated, in‐channel river hydraulics in the LYR from 8.50 to 3,126 m 3 /s (0.06 to 22 times bankfull discharge).…”

Evaluation of the Methodology to Assess the Influence of Hydraulic Characteristics on Habitat Quality

“…Therefore, it is important to know the impact of the hydromorphological characteristics of the stream on the aquatic ecosystem [3,4]. Abiotic characteristics, together with habitat quality, form the basis for assessing the habitat availability [5,6]. The set of these relationships is the basis for a comprehensive environmental assessment.…”

Model-Based Analysis of Macrophytes Role in the Flow Distribution in the Anastomosing River System

“…Manning's equation used in this study is widely accepted methodology in stream resistance evaluation, especially in vegetated areas [46], and was successfully incorporated in numerous researches investigating the impact of vegetation on water flow, depth and velocity [32,33,47,48]. A quantitative comparison of calibrated Manning's coefficient values with those reported in the literature can be made, linking plant traits (height and flexibility) to roughness.…”

“…Here, the MFRM is optimized using actual measured entry discharge into each single channel of the complex anastomosing system, which is a significant advantage of this study. Gibson and Pasternack [33] developed a 1D model for anastomosing reach of the River Yuba where only one bifurcation was modeled. With no measurements on discharge division between the channels, the authors found 1D model simulations underwhelming and split flow modeling to be complex.…”

“…However, they declared no field measurements on the flow distribution and river cross-sections, and limited their research only to one bifurcation without taking into account the detailed role of vegetation in flow distribution. Another attempt of anastomosing river modeling was made by Gibson and Pasternack [33], who developed a 1D and 2D model for three morphologically different reaches among which, anastomosing could be found. Although only one bifurcation was modeled, the authors found 1D model simulations underwhelming and split flow modeling to be an intermediate level of complexity.…”