Identification

Title

Large river confluence numerical model output (NERC grant NE/I023228/1)

Abstract

This dataset contains numerical model output of a morphodynamic and sedimentological simulation of a large river confluence based loosely on the Jamuna-Ganges junction in Bangladesh. The work was carried out as part of a joint project between the Universities of Birmingham, Southampton and Exeter. "The sedimentology of fluvial megascours" was a scientific research project funded by NERC. One aspect of the project was to undertake numerical simulations (the data described here) with which to compare with river bed bathymetry data (collected using a multibeam echosounder) and sub bottom seismic profiling data (collected using a surface tow boomer and chirp system). The data has been accepted for a publication in the journal 'Sedimentology' which will be published in 2018 with the title 'The Sedimentology of channel confluences'.

Resource type

nonGeographicDataset

Resource locator

http://www.bgs.ac.uk/services/ngdc/accessions/index.html#item110053

function: download

http://www.bgs.ac.uk/services/ngdc/citedData/catalogue/94da442e-2027-4ee0-b664-9f251eec681f.html

function: information

Unique resource identifier

code

http://data.bgs.ac.uk/id/dataHolding/13607328

codeSpace

Dataset language

eng

Spatial reference system

code identifying the spatial reference system

Classification of spatial data and services

Topic category

geoscientificInformation

Keywords

Keyword set

keyword value

originating controlled vocabulary

title

GEMET - INSPIRE themes

reference date

date type

publication

effective date

2008-06-01

Keyword set

keyword value

Bathymetry

Seismic data

Sedimentary geology

Rivers

originating controlled vocabulary

title

BGS Thesaurus of Geosciences

reference date

date type

revision

effective date

2011

Keyword set

keyword value

NERC_DDC

Geographic location

West bounding longitude

East bounding longitude

North bounding latitude

South bounding latitude

Temporal reference

Temporal extent

Begin position

End position

2018-05-01

Dataset reference date

date type

creation

effective date

2018-05-01

Frequency of update

notApplicable

Quality and validity

Lineage

The morphodynamics and deposits of a large river confluence were simulated using a physically-based, two-dimensional, numerical model (HSTAR) that represents water flow, sediment transport (for two size fractions; sand and silt), bank erosion and floodplain formation. The model has been described in detail and evaluated elsewhere (Nicholas et al., 2013), and shown to be suitable for representing a range of large sand-bed rivers (Nicholas, 2013). In particular, unit bars, the key building block of sand-bed rivers, are an emergent characteristic of the simulations, resulting directly from patterns of modelled erosion and deposition, although it should be noted that smaller-scale bedforms (e.g. dunes and ripples) are not resolved within the model. HSTAR solves the two-dimensional, depth-averaged, shallow water equations written in conservative form. Model equations are solved on a structured grid (resolution δx, δy) within which each grid cell is defined as either active river bed or floodplain (including vegetated islands). For active river bed cells, total sand transport (bedload and suspended load) is modelled using the Engelund-Hansen (1967) transport law. For hydraulic roughness, a constant Chezy value of 50 m0.5s-1 is used in all channels and 15 m0.5s-1 on vegetated surfaces. The model domain was set-up to be broadly comparable to the confluence of the Jamuna and Ganges rivers in Bangladesh. All simulations were conducted using a model domain 66 km long (x direction) by 48 km wide (y direction). This resulted in a model with 1100 × 800 cells, each measuring 60 m long by 60 m wide. The initial width of the two simulated channels upstream of the confluence was 3.6 km and 1.8 km, respectively, with initial channel width downstream of the confluence being c. 4 km. The planform configuration of the model was also similar to the field site, with the channel downstream of the confluence forming a 27° angle to the axis of the major incoming channel. Bank erosion rates are modelled as the product of the bank gradient, the total rate of sediment transport parallel to the bankline, and a dimensionless bank erodibility constant. To capture the planform change observed in the field, the bank erodibility constant was set to be lower (i.e. stronger banks) for the smaller upstream tributary channel and the channel downstream of the confluence, but higher (i.e. weaker banks) for the larger incoming tributary. Finally, the simulated flow regime was also broadly similar to the field site, with low flow and peak discharges for the larger channel of 4000 m3s-1 and 80000 m3s-1, respectively, to reflect the monsoon-dominated regime. Flows in the smaller channel were 50% of that in the main channel. Simulated inflow conditions consisted of a series of regular symmetrical hydrographs, where discharge (Q ) as a function of time is: Q = Qlow + (Qmax - Qlow) ((1+sin(2?T-?/2))/2)3.5 where T is time normalised by the hydrograph duration (i.e. T increases from 0 to 1 over the course of the hydrograph), Qlow is the low flow discharge, and Qmax is the flood peak discharge. Simulations ran for a sequence of 150 annual flood hydrographs. The data consists of 150 output files, one for each simulated flood event. Each file has 6 columns of data; 1) x coordinate (m) 2) y coordinate (m) 3) elevation (m) - with 999 = no data (effectively, not an active part of the model domain) 4) depth (m) 5) unit discharge in x direction (m^2s^-1) 6) unit discharge in y direction (m^2s^-1)

Conformity

Conformity report

specification

title

INSPIRE Implementing rules laying down technical arrangements for the interoperability and harmonisation of Geology

reference date

date type

publication

effective date

2011

degree

false

explanation

See the referenced specification

Conformity report

specification

title

Commission Regulation (EU) No 1089/2010 of 23 November 2010 implementing Directive 2007/2/EC of the European Parliament and of the Council as regards interoperability of spatial data sets and services

reference date

date type

publication

effective date

2010-12-08

degree

false

explanation

See http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2010:323:0011:0102:EN:PDF

Data format

name of format

DAT files

version of format

Constraints related to access and use

Constraint set

Limitations on public access

Constraint set

Limitations on public access

The copyright of materials derived from the British Geological Survey's work is vested in the Natural Environment Research Council [NERC]. No part of this work may be reproduced or transmitted in any form or by any means, or stored in a retrieval system of any nature, without the prior permission of the copyright holder, via the BGS Intellectual Property Rights Manager. Use by customers of information provided by the BGS, is at the customer's own risk. In view of the disparate sources of information at BGS's disposal, including such material donated to BGS, that BGS accepts in good faith as being accurate, the Natural Environment Research Council (NERC) gives no warranty, expressed or implied, as to the quality or accuracy of the information supplied, or to the information's suitability for any use. NERC/BGS accepts no liability whatever in respect of loss, damage, injury or other occurence however caused.

Responsible organisations

Responsible party

contact position

School of Geography, Earth and Environmental Sciences

organisation name

University of Birmingham

full postal address

Birmingham

B15 2TT

email address

not available

responsible party role

pointOfContact

Responsible party

contact position

School of Geography, Earth and Environmental Sciences

organisation name

University of Birmingham

full postal address

Birmingham

B15 2TT

email address

not available

responsible party role

principalInvestigator

Metadata on metadata

Metadata point of contact

organisation name

British Geological Survey

full postal address

Environmental Science Centre,Keyworth

NOTTINGHAM

NG12 5GG

United Kingdom

telephone number

+44 115 936 3100

email address

enquiries@bgs.ac.uk

responsible party role

pointOfContact

Metadata date

2021-05-11

Metadata language

eng