Simone Bizzi

In collaboration with:Dr Andrea Nardini Technical Director of CIRF (Italian

Centre for River Restoration)

Model and evaluate geomorphology under different

catchment management strategies

What is Geomorphology?

“..the study of sediment sources, fluxes and storage within the river catchment and channel over short, medium and longer timescales and of resultant channel and floodplain morphology” (Newson and Sear 1993)

Geomorphology and river management?

• Annual expenditure on Flood Defence > £500 million

• WFD requirement to maximize habitat quality

Aims of the research

Model and evaluate geomorphological features under different catchment managements strategies

National Level

Regional/River Basin Level

Catchment/Coastal cell level

Community Level

Site/System level

Why River Habitat Survey?

•10 years of experiences and more than 10000 samples only in England and Wales

•Assessments and decisions are taken using this dataset

•Feedbacks for the next versions

Is it the database suitable?

Problems to face

•Limited information in the variables

•Dynamic system in space and time

•Typology: Every river has its behaviour

Index

(Targets – Geomorphological Features)

Model approach

More experiences in literature Geomorphology (CAESAR,REAS, HEC-RAS ..)

•They require detailed and specific data

•Most of the time not catchment scale

•Evaluation phase most of the time is missing

National Level

Regional/River Basin Level

Catchment/Coastal cell level

Community Level

Site/System level

Modelling Evaluating

Information

(Causal Factors)

Evaluation

Model approach

Modelling Evaluating

Phase 1: A cluster analysis able to find pattern in the data and structured them in a way suitable for the evaluation

Information

(Causal Factors)

EvaluationIndex

(Targets – Geomorphological Features)

Model approach

Phase 2: A classification model able to give an output suitable for an evaluation

Modelling Evaluating

Information

(Causal Factors)

EvaluationIndex

(Targets – Geomorphological Features)

RHS site

Geomorphological Features (targets):

•Numbers of Bars

•Numbers of Pools and Riffles

•Type of Bank vegetations

•Numbers of woody debris

•Bankfull width

CONCEPTUALIZATION

RHS site

Natural variables (Causal Factors )

•Slope

•Flow Regime

•Geology

CONCEPTUALIZATION

RHS site

CONCEPTUALIZATION

Percentage of Land Use in the sub-catchment (Causal Factor ):

•Vegetated

•Urban

•Improved Grass Land

•Arable

RHS site

CONCEPTUALIZATION

Percentage of area in the sub-catchment obstructed by dams or artificial reservoirs (Causal Factor )

d1

d2

d3

d4

RHS site

CONCEPTUALIZATIONRHS sitesLevel of modification in the sites and upstream (Causal Factors)•Hard Modification :

ResectioningBank and channels reinforcementsEmbankments

•Soft Modification: WeirsBridgesford..

•Culverts

d1

d2

d3

d4

RHS site i

CONCEPTUALIZATION

xi (t+1)= f( uRHS,i(t),ucat,i(t), Nat(t) )

xi = f( uRHS,i,ucat,i ,Nat)

STEADY STATE

Clustering Step

Clustering Step

Natural Variables (VERTICAL path) Vs Anthropogenic Variables (HORIZONTAL path)

Clustering Step

C1

C3

C2

Riffles and

Pools

Bars Bank vegetation

Mean C1 1.74 1.32 17.5

Mean C3 4.78 9.15 25

Model capability

?

?

C1

C3

Arable Urban Land

Vegetated

Grass land

Mod. Up stream

Mod. in the site

C1 mean 47 7 23 20 10 16

C1 std 15 7 9 10 6 11

C2

 SCENARIOSrate (% in Class

C1)

Scenario zero (untouched) 100

Reduced Hard Interventions in the site

(80%) 85

Reduced Hard Interventions in the site

and up-stream (80%) 66

Land Use changes (-50% Arable - 20% Urban

->Vegetated) 87

All together 24

?

?

C1

C3

C2

Model capability

 Scenarios

rate (% in Class

C1)P(x/C1)

P(x/C2)

P(x/C3)

Scenario zero (untouched) 100 0.9 0.05 0

Reduced Hard

Interventions in the site and up-

stream (80%) 66 0.59 0.27 0.03

?

?

C1

C3

C2

Model capability

• The weakness of a site specific approach

• Flexible Geomorphological tool at national level

• RHS limits

Conclusions

Future Directions

• Assessing the feasibility to add biology

• Developing a “site specific” case study to overcome some limitations intrinsic in the national level

• Analysing the level of “integrability” between these two different approach

Thank you for your attention!

s.bizzi@sheffield.ac.uk