Hydrogeomorphic Assessment Research Articles

An effective geospatial-based flash flood susceptibility assessment with hydrogeomorphic responses on groundwater recharge

Floods are one of the most common natural disasters, resulting in the extensive destruction of infrastructure, property, and human life. The destructive potential of a flood depends on numerous factors, including the size of the flood, the rate of flooding, the time it takes for the water to move through a given area, the river's planform and cross-section geometry, and other similar factors. The present study is a unique analysis of flood mapping that was accomplished with the help of the Analytical Hierarchy Process (AHP), Frequency Ratio (FR), and hydrogeomorphic response to floods by integrating geospatial analysis and unit stream power modeling. The Indus catchment region of Pakistan is where the subject topic is put into practice. According to the hydrologic analysis of the yearly peak discharge, the hydro-station in Gilgit-Baltistan can move boulders measuring up to 0.5 m in height during significant flooding. On the other hand, there will be no change to the geometry of the cross-section throughout 1980–2020 in Gilgit-Baltistan. The flood susceptibility map is constructed using data from twelve influencing parameters, including elevation, proximity to the drainage network, slope, drainage density, geomorphology, rainfall, the curvature of the topography, flow accumulation, geology, land use, Topographic Wetness Index (TWI), and Stream Power Index (SPI). The area under the curve (AUC) approach, which demonstrates a substantial degree of accuracy (85% and 83%), is utilized to evaluate the effectiveness of the AHP and FR. The current study fills the gaps between the geospatial approach and the hydrogeomorphic assessment of flood to determine flood susceptibility.

Managing urban riverscapes: An assessment framework to integrate social-ecological values and physical processes

The services that rivers provide and how they affect the landscape plays a dominate role in urban planning and development. Urban riverscapes, which consist of stream channels, their floodplains, biotic communities, and manmade features, are complex social-ecological and hydrogeomorphic systems. Yet, despite recognition of their place and value, rivers are often degraded in urban settings. Successfully managing urban riverscapes requires improved methods to assess them and to more effectively link stressors to values, and to incorporate these considerations in planning. Assessment of urban riverscapes’ physical condition and function—a hydrogeomorphic assessment—is necessary to make these links, and inform more appropriate management strategies for sustainable and valued riverscape systems. The framework and methods used for such an assessment should be appropriate to the urban context, insofar as they are applicable to a range of streams from lightly degraded to highly utilized or constructed. Above all, the framework must prioritize the connection of human communities to riverscapes. In this article, we outline a framework for urban riverscape assessment which considers four facets of urban riverscapes: human values, hydrology, geomorphology, and ecology. The four facets, assessed across multiple nested scales, provide a flexible basis for context-driven hydrogeomorphic assessment, which is vital to informing better planning and management of urban riverscapes. The framework can be integrated with other facets (e.g. geochemical, aquatic ecology) depending on the scope of the assessment. By linking intrinsic, relational, and use-based values to physical conditions, watershed managers can select relevant and measurable indicators that directly inform interventions in the riverscape, catchment, or urban zones to improve riverscape function and urban vitality through planning mechanisms. This assessment framework facilitates dialogue between managers, practitioners, scientists, and the community; enabling technical and non-technical inputs to the development of assessment criteria, and a shared vision to inform targets and goals.

Hydrogeomorphic indicators of wetland health inferred from multi-temporal remote sensing data for a new Ramsar site (Kaabar Tal), India

Wetlands form an important and dynamic ecosystem, and therefore, need continuous monitoring. We have developed a framework to assess the status of wetland health based on hydrogeomorphic characteristics and vegetation dynamics and have implemented it on a newly designated Ramsar site, Kaabar Tal, a large floodplain wetland in Ganga Plains, eastern India. The study has attempted to integrate the hydrological, geomorphological, and ecological concepts and tools to develop the protocols for a hydrogeomorphic assessment of wetland health. We have used multi-temporal Landsat imageries to define several health indicators based on water-spread area, geomorphology, and vegetation and have integrated them to compute wetland health index (WHI) scores. These health indicators correspond to a range of spatial scales – landscape (wetland) scale, ecosystem (sub-wetland) scale, and local (pixel) scale and individually represent different hydrogeomorphic and ecological functions as well as dynamics of a wetland. We have also presented four different wetland health scenarios based on dominating health indicator and two integrated scenarios representing the best and the worst WHI scores in all four scenarios. Our results show that the Kaabar Tal is in a degraded state and the degree of degradation varies spatially within the wetland. Agriculture is the prime factor for its degradation, augmented by decreasing rainfall and anthropogenic drainage reorganization. Based on our data analysis, we have suggested several recommendations to restore the health of this wetland. The framework presented in this work has a potential to understand the relationship between hydrodynamics and ecological functions in wetland systems in different hydro-climatic settings.

Hydrogeomorphic assessment of badlands in part of the Mandakini River watershed, Chitrakoot, India

Badlands are a hydrogeomorphological feature with operative processes leading to intense erosion. This study utilizes the morphometric methods with the help of remote sensing data in a GIS environment to determine the characteristics of the badlands of Mandakini River watershed and their interpretation to explore the factors responsible for the formation of the typical landforms. Objective interpretation of morphometric data of badlands with the help of statistical Pearson’s correlation coefficient (PCC) and dendrogram cluster may be made to emphasize the controlling factors. The morphometric parameters like the total number of streams (Nu), bifurcation ratio (Rb), drainage density (Dd), drainage frequency (Fs), drainage texture (Dt), and infiltration number (If) and their correlation in the study area plays a significant role in the advancement of rills and gullies. In the present area, the total number of streams (Nu) is very significantly related with the lengths of the first-order (L1), the second-order (L2), and the third-order streams (L3) along with the total stream length of all orders (Lu) in the third-order and the fourth-order sub-watersheds. Bifurcation ratio (Rb) is strongly correlated with L1, L2, L3, L4, and drainage texture (Dt) in the fourth-order sub-watershed. These correlations insinuate a tectonic influence in the basin and show an ultrafine drainage texture that ultimately forms badland topography. The relation between Dd-Lg-C-If-Rn produces a self-enhancing system of badland development, which promotes erosion in the area under study. These correlations provide a well-figured observation of the sub-watershed that, due to the increase in infiltration number (If), the drainage density (Dd) also increases, which leads to enhancement of channel cutting and erosion rates (low Lg and C value). This correlation coefficient of Rn is moderately low, indicating a single storey type of badlands. The badlands seem to have formed owing to setting up of self-enhancing erosive system on paleo wetlands, as evidenced by the presence of calcretes. Calcretes have been related to the presence of wetlands’ conditions. These have been related to fall in water levels, therefore, indicating much higher water levels nearly close to ground surfaces before setting up badlands conditions. Thus, the badlands which have shallow calcretes horizons can be said to have been wetlands in the past.

Wetland Functional Responses to Prolonged Inundation in the Active Mississippi River Floodplain

The Mississippi River experienced historic flooding during 2019, inducing >150 days of floodplain wetland inundation. We evaluated flood effects using repeated measures of hydrogeomorphic (HGM) wetland assessment variables prior to the flood (October 2018), immediately post-flood (August 2019) and one year after initial assessment (October 2019). The flood had little/no impact on 11 of 13 assessment variables, but altered the abundance of woody debris and forest floor litter. Immediately after the flood, these changes decreased the functional capacity of wetlands to 1) detain floodwater (mean − 9.7% reduction) and 2) precipitation (−17.3%); 3) cycle nutrients (−7.5%); and export organic carbon (−23.8%). Subsequent sampling documented the detain precipitation function returning to pre-flood conditions. The export organic carbon function also improved, yet remained below pre-flood levels. Other functions will likely require additional recovery time due to the persistence of accumulated excess woody debris. Across all sample intervals, floodplain wetlands displayed high wetland function capacities and appear resilient to surface water inundation. This analysis highlights the utility of the HGM assessment to detect responses to changing environmental conditions over short time intervals. The study also emphasizes the need to incorporate metrics with appropriate impact-response characteristics when developing and implementing ecological assessments.

Hydro-geomorphic assessment of erosion intensity and sediment yield initiated debris-flow hazards at Wadi Dahab Watershed, Egypt

ABSTRACT This study attempts to assess slope and channel erosion for modelling their implications on debris-flow occurrences in Wadi Dahab Watershed (WDW). Remote sensing and Geographic Information System (GIS) were integrated to appraise erosion rates from a hillslope and channel storage throughout WDW. A mass-wasting database was built initially for modelling hazard zones and validating the final map using a bivariate statistical analysis. An Erosion Hazard Model (EHM) was developed to evaluate the erosion intensity and sediment yield throughout WDW and to prognosticate the hazard zones due to debris-flows. The EHM was developed based on hydrological and geomorphic controls which are responsible for disintegrating bedrocks, delivering detritus downslopes, and accelerating debris through channels. Multi-source datasets, including topographic and geologic maps, climatic, satellite images, aerial photographs, and field-based datasets, were used to derive factors associated with the hydro-geomorphic processes. A spatial prediction of erosion intensity was obtained by the integration of both static and dynamic factors generated hazards in GIS platform. The erosion intensity map classifies WDW relatively to five intensity zones in which the most hazardous zones are distributed in steep sloping terrains and structurally controlled channels covered by metamorphic and clastic rocks. The erosion intensity map was correlated and tested against the debris-flows dataset which was not used during the spatial modelling process. The statistical correlation analysis has confirmed that the debris-flow locations increase exponentially in the high erosion intensity zones. The holistic integration approach provides the promising model for forecasting critical zones prone to erosion intensity and their associated hazards in WDW.

Geospatial mapping of flood susceptibility and hydro-geomorphic response to the floods in Ulhas basin, India

Flood is a common natural disaster that causes immense damage to the natural environment, construction and casualties every year around the world. The effectiveness of flood is a function of several criterions such flood power, magnitude, frequency, duration of the flow, changes of the planform and cross-section geometry in a river etc. Alternatively, the prevention of flood depends on assessment of various factors which are related to flood occurrence. In an international scale, it may not be possible to prevent flooding by some full scale assessment of environmental factors. However, deterrence of regional floods can easily be done through flood susceptibility mapping. The present work represents an innovative analysis of flood mapping through the analytical hierarchy process (AHP) and hydro-geomorphic response to the floods by implementing geospatial analysis and unit stream power modelling. The subject field is applied in Ulhas catchment, India. The hydrologic assessment of yearly peak discharge shows that the hydro-station located at Badlapur is capable to transport upto 0.5 m boulder during extreme flood events. However, there is no transformation of the cross-section geometry during 2005–2012 at Badlapur. The flood susceptibility map is constructed based on twelve influencing parameters, i.e. elevation, slope, distance from drainage network, geomorphology, drainage density, flow accumulation, rainfall, land-use, geology, stream power index, topographic wetness index and curvature of the topography. Established along the resultant flood susceptibility map, it is found that about 25% area of the Ulhas catchment is under very high flood susceptibility. The efficiency of the analytical hierarchy process is examined by employing area under the curve (AUC) method which shows considerable accuracy (84%). The present study bridges the gap between the hydro-geomorphic assessment of the flood and the geospatial approach towards flood susceptibility.

Comparing tiers of a multi-tiered wetland assessment in the Prairie Pothole Region

Wetland assessment has been shown to be an important tool in understanding the condition and function of the world’s wetlands, and use of muli-tiered assessment strategy has been recommended. In order to evaluate the performance of each tier of a multi-tiered wetland assessment strategy, we sampled 255 seasonally-ponded wetlands in the Missouri Coteau, the most wetland dense ecoregion in the Prairie Pothole Region. We assessed the condition of each study wetland using four sampling methods and models (tiers) of increasing levels of effort and complexity: (1) a level 1 assessment using the geographic information system-based Landscape Wetland Condition Analysis Model (LWCAM); (2) a level 2 assessment using the North Dakota Rapid Assessment Method (NDRAM); (3) a level 3- assessment using the vegetative-based Floristic Quality Index (FQI) and (4) a level 3 assessment consisting of a Hydrogeomorphic (HGM) Model functional assessment. We compared assessment tiers to determine how similar the different levels of assessment ranked sites either by condition or function. Both the NDRAM and FQI assessments, though very different in wetland characteristics assessed, provided similar condition rankings as the more intensive level 3 HGM assessment (89 and 90% similar, respectively). Additionally, the FQI was 86% similar to the level 2 NDRAM, indicating that these two assessment methods have utility in assessing wetlands similar to a HGM assessment. Information from this study can be used as a tool for determining need specific, financial, and time appropriate wetland sampling methods.

A hydrogeomorphic assessment of twenty‐first century floods in the UK

AbstractThe occurrence of devastating floods in the British uplands during the first two decades of the twenty‐first century poses two key questions: (1) are recent events unprecedented in terms of their frequency and magnitude; and (2) is climate and/or land‐use change driving the apparent upturn in flooding? Conventional methods of analysing instrumental flow records cannot answer these questions because upland catchments are usually ungauged, and where records do exist they rarely provide more than 30–40 years of data. In this paper we analyse all lichen‐dated upland flood records in the United Kingdom (UK) to establish the longer‐term context and causes of recent severe flooding. Our new analysis of torrential sedimentary deposits shows that twenty‐first century floods are not unprecedented in terms of both their frequency (they were more frequent before 1960) and magnitude (the biggest events occurred during the seventeenth–nineteenth centuries). However, in some areas recent floods have either equalled or exceeded the largest historical events. The majority of recent floods have been triggered by torrential summer downpours related to a marked negative phase of the summer North Atlantic Oscillation (NAO) between 2007 and 2012. It is of concern that historical data suggests there is far more capacity in the North Atlantic climate system to produce wetter and more prolonged flood‐rich periods than hitherto experienced in the twenty‐first century. Looking forwards, an increased likelihood of weather extremes due to climate change means that geomorphological based flood series extensions must be placed at the centre of flood risk assessment in the UK uplands and in similar areas worldwide. Copyright © 2015 John Wiley & Sons, Ltd.

Freedom space for rivers: a sustainable management approach to enhance river resilience.

River systems are increasingly under stress and pressure from agriculture and urbanization in riparian zones, resulting in frequent engineering interventions such as bank stabilization or flood protection. This study provides guidelines for a more sustainable approach to river management based on hydrogeomorphology concepts applied to three contrasted rivers in Quebec (Canada). Mobility and flooding spaces are determined for the three rivers, and three levels of "freedom space" are subsequently defined based on the combination of the two spaces. The first level of freedom space includes very frequently flooded and highly mobile zones over the next 50 years, as well as riparian wetlands. It provides the minimum space for both fluvial and ecological functionality of the river system. On average for the three studied sites, this minimum space was approximately 1.7 times the channel width, but this minimum space corresponds to a highly variable width which must be determined from a thorough hydrogeomorphic assessment and cannot be predicted using a representative average. The second level includes space for floods of larger magnitude and provides for meanders to migrate freely over a longer time period. The last level of freedom space represents exceptional flood zones. We propose the freedom space concept to be implemented in current river management legislation because it promotes a sustainable way to manage river systems, and it increases their resilience to climate and land use changes in comparison with traditional river management approaches which are based on frequent and spatially restricted interventions.

Developing an index of wetland condition from ecological data: An example using HGM functional variables from the Nanticoke watershed, USA

Demand for data on the ecological condition of wetlands is increasing as state and federal management programs recognize its value in reporting on the ambient condition of the resource, targeting restoration and protection efforts, evaluating the effects of mitigation and restoration practices, supporting regulatory decisions, and tracking the impact of land use decisions. We developed an approach for generating a single measure of wetland condition from ecological variables used in hydrogeomorphic (HGM) assessment. An Index of Wetland Condition (IWC) was developed from HGM field data collected to assess freshwater, non-tidal flat, riverine, and depression wetlands in the Nanticoke River watershed. The HGM variables were screened and scored based on a range check, responsiveness, and metric redundancy, employing a method used to develop indices of biotic integrity. Weights of the individual variables were adjusted to reflect our understanding of wetland ecology and to include variables that represented the vegetation, hydrology, and buffer of a wetland. The final IWC score discriminated high, medium, and low site disturbance classes in flat and riverine wetlands and high and low disturbance classes in depressions, one-way ANOVA F-values ranged from 44.5 to 79.1 (all p <0.0001). The combination of the IWC and HGM assessments provides a comprehensive evaluation of the wetland resource. HGM produces information on specific wetland functions. The IWC concisely conveys the ecological condition of the resource and maximizes the utility of the data collected in an HGM assessment.

Assessment of wetlands in the Upper Juniata watershed in Pennsylvania, USA using the hydrogeomorphic approach

This paper reports on the ecological status of wetlands in the Upper Juniata watershed in Pennsylvania, USA, as determined by employing the hydrogeomorphic (HGM) approach. HGM assessment provides a measure of the potential functional performance of a single wetland for up to 11 functions, depending on the subclass. Functional Capacity Index (FCI) scores calculated for each function range between a score of 1 (indicates the site is performing at optimum levels) and a score of 0 (indicates the site is not performing the function). Mean scores for all functions for the wetland resource in the Upper Juniata ranged from 0.48–0.63, except for Long-term Surface-Water Storage (0.39) and Characteristic Hydrology (0.85). Cumulative Distribution Function (CDF) plots were fairly linear over most of the distribution for all functions, indicating that the FCI scores were evenly distributed over the population. Several of the plots flattened at the upper and/or lower ends of the curves, indicating that a very small proportion of the wetland area had the highest and lowest scores. Clustering of the 69 riverine and slope sites using the FCI scores from the three functions with the most well-developed models resulted in the formation of four Functional Status Groups (FSGs). Groups 1 and 2 represented relatively high functioning groups of sites. They were differentiated by an exceptionally high Plant Community Function in Group 1 that differed significantly from the low value in Group 2. FSG’s 3 and 4 represented relatively low functioning groups of sites and were differentiated by a significantly high Vertebrate Community Function in Group 3. We defined three reference domains (Natural, Agricultural, and Developed) based on predominant land cover. Sites of any given FSG were distributed across the reference domains, but there were some differences in distribution. Sites in the Natural Domain were much more likely to be in the higher functioning FSGs, while the Agricultural Domain was dominated by sites with an overall low level of functioning. Sites in the Developed Domain are equally distributed across the four FSGs. In summary, we demonstrated how HGM assessment might be employed to describe the functional status of the wetland resource in a watershed. We also demonstrated how the results of the assessment could be (1) used to evaluate the efficacy of the models comprising the HGM assessment and (2) combined with other data to identify relationships that could be used to develop management approaches.

Applying wetland reference data to functional assessment, mitigation, and restoration

This study demonstrates an approach for rapidly collecting quantitative field data on reference wetland sites and using those data to assess functions (ecological processes) in wetlands. We demonstrate the hydrogeomorphic (HGM) assessment procedure by identifying ecological functions performed by mineral soil wet fiats, obtaining quantitative field data from 19 wet fiats (reference sites) in southeastern North Carolina, and modeling wetland functions using variables derived from those field data. We chose a subset of the 19 reference sites to demonstrate how HGM assessment can be used to measure ecosystem functions before and after a project site is altered and the degree to which ecosystem restoration can compensate for a reduction in functions caused by a project's impact. We also illustrate how HGM assessment can be used to determine the minimum area over which restoration should be applied to achieve a no-net-loss in function objective. This minimum area can be determined by dividing the degree to which a function is reduced through project alteration by the degree to which a function is increased through restoration. The ratio of wetland area restored to wetland area altered by a project impact (compensatory mitigation ratio) varies among functions and is influenced by (1) the magnitude to which any given function occurs at a project site both before and after the site is altered, (2) the magnitude to which any given function occurs at a compensatory mitigation site both before and after restoration is applied, and (3) the rate at which any given function is restored.