چكيده لاتين :
Introdoction
Fluvial geomorphology has delivered empirical tools that have proved useful for river management in the last decade. The term of hydromorphology is considered to any modifications to flow regime, sediment transport, river morphology, and lateral channel mobility. Channel classification is one tool that is focuses on assessing the effects of natural and anthropogenic disturbances of the landscape in order to understand past response, determine current conditions, and predicts likely responses to future disturbance, including land man- agement and restoration activities. Numerous geomorphic classifications have been developed for rivers over the past century. Types of stream classification are summarized to Stream Order, Process Domains, Channel Pattern, Channel–Floodplain Interactions, Bed Material and Mobility, Channel Units, Hierarchical Classifications and Statistical Classifications. In this paper, the Morphological Quality Index (Rinaldi et al, 2013) carried out lavij stream. The Lavij catchment is located in Nour Township, Mazandaran province. The altitude of the Lavij catchment varies from a maximum of 3359 m to 100 m on the valley floor.
Material and method
The first phase of MQI method is aimed at subdividing the river network into relatively homogeneous reaches, with no significant changes in valley setting, channel slope, imposed flow and sediment load. This phase consist of four steps. In step 1, a basic investigation of geology, geomorphology, climate, and the land use of the catchment is carried out. In step 2, lateral confinement is analyzed, and three valley settings are differentiated: confined, partly confined, and laterally unconfined channels. In step 3, channel morphology is analyzed in according to classifications of river morphologies. Step 4 considers additional discontinuities to further subdivide the stream reaches.The final product of this phase is the subdivision of the river network into reaches that are relatively homogeneous in terms of channel morphology, lateral confinement, hydrology, and other characteristics, reflecting no significant changes in the flow or sediment load (Brierley and Fryirs, 2005). The aspects are considered for the assessment of the morphological quality of river reaches including: (i) continuity of river processes (longitudinal and lateral continuity); (ii) channel morphological conditions (channel pattern, cross section configuration and bed substrate) and (iii) vegetation. These aspects are analyzed in terms of three components: (i) the geomorphological functionality of river processes and forms; (ii) artificiality; and (iii) channel adjustments.
For each indicator, the scores to be assigned to each answer are reported on the evaluation form, proportionally to the degree of alteration, that is, in increasing order from A (score 0) to C (maximum score for that indicator). A total score was computed as the sum of scores across all components and aspects. A stream Morphological Quality Index (MQI) varying from 0 (minimum quality) to 1 (maximum quality).
Results
Six reaches are examined by MQI method in lavij stream and is summarized as follows. The reach 1 is a mountain stream along a partly confined channel, with a mean channel width of 4 m and slope of 0.08m/m. the channel bottom alternates subreaches with cobble and gravel and a step-pool configuration. There is a little alteration compared to the expected conditions. The final result is MQI = 0.85 and the reach is classified as very good.
The reach 2, located partly confined stream. Channel width is 4m and average channel slope is 0.05 m/m. The elements which determine alterations of morphological quality are in-channel sediment removal and removal of large woody debris. The final result is MQI = 0.76 and the reach is classified as good.
The reach 3 is confined mountain stream, with a mean channel width of 6 m and slope of 0.04 m/m. The channel is single thread, banks are composed of rock outcropping. Channel bed is consisted with cobble and gravel and a step-pool configuration. There are no significant alterations in channel. The final result is MQI = 1 and the reach is classified as very good.
Reaches 4and 5 are partly confined stream, with a mean chaanel width 8 m and slope 0.03 m/m. channels is single thread with with alternate bars. There are no significant alterations compared to the expected conditions. The final result, in both reaches, is MQI = 0.98, therefore the reach is classified as very good.
The reach 6 is a partly confined river which flows within a plain. The river displays a braided morphology. The main elements of alteration are: (1) there is a big open check dam (2) the channel bed (incision > 6 m), mainly related to past intensive ( < 20 year) mining activity responsible for some significant channel adjustments. (3) Some localized artificial elements in the reach (bridge, sills, drop, etc.).Therefore the channel changes indicators (CA1, CA2 and CA3) result as having maximum scores.The final result is MQI = 0.22, therefore the reach is classified as poor.
Conclusion
The MQI results show that river reaches with heavy alterations were expected to fall into the lower categories and stream reaches with low alterations were expected to fall into the higher categoriesvice.The results of MQI with River Style Framework, in reaches 1 to 5, is consistency.
