The Economist - USA (2022-06-11)

The Economist June 11th 2022 Science & technology 79

Floodwarnings

Earthshaking

O

njuly14th 2021 a floodtorethrough

theAhrvalley,innorth­westGermany.

Noneofthetownsuponwhichitvisited

deathanddestructionhadhadwarningof

howbaditwouldbe.Thatwarningshould

havebeen supplied byautomatic flood­

levelgaugessitedupstream,intheriverit­

self.Itwouldhavepermittedevacuationof

housesinparticulardanger.Butthegauges

weredestroyedbythetorrentbeforethey

couldsupplymeaningfulinformation.

Relyingoninstrumentswhichare,by

their very location, vulnerable to being

swept away, is hardly an ideal approach to

tracking  impending  floods.  But  Michael

Dietze of gfz, the German Research Centre

for  Geosciences,  suggests  an  alternative.

On  May  26th  he  proposed  to  the  annual

meeting of the European Geosciences Un­

ion, in Vienna, that a network of seismom­

eters of a sort more usually employed to re­

cord earthquakes might do the job.

Seismometers  record  minute  ground

movements.  Their  purpose  is  to  listen  for

vibrations  generated  by  tectonic  activity,

usually far away. But on that particular day

a rather different set of useful signals came

to  a  seismometer  operated  by  Germany’s

Central  Seismological  Observatory.  This

was, fortuitously, located 1km north of the

Ahr’s  streambed.  And  it  picked  up  vibra­

tions caused by the passing deluge.

They were not completely unexpected.

Research by Dr Dietze and others had alrea­

dy  established  that  seismometers  several

kilometres  from  fast  mountain  rivers  can

detect the violence with which the waters

of a swollen stream pound the banks, and

also  the  din  of  millions  of  pebbles,  boul­

ders  and  other  debris  bouncing  along  the

bottom  during  a  flood.  However,  when

they studied this particular seismometer’s

output,  he  and  his  colleagues  also  saw  a

third,  more  gradual  effect:  a  tilting  of  the

ground on which the instrument was rest­

ing. This was caused by deformation of the

local  crustal  rocks  as  a  result  of  the  sheer

weight  of  the  bulge  of  water  speeding

through  the  valley.  They  had  seen  some­

thing  similar  before,  but  only  as  a  conse­

quence of typhoons hitting small islands.

Together, says Dr Dietze, these three sig­

nals provided a wealth of information, al­

beit retrospective, about the flood’s behav­

iour  from  the  moment  it  came  within  lis­

tening range, about 2km upstream, until it

had  passed  the  point  closest  to  the  seis­

mometer,  after  which  grid  power  failed

andthemeasurementsstopped.  Both  the

tilting  and  the  vibrations  revealed  the

flood’s  direction;  the  debris  noise  gave  an

indication  of  how  much  damage  to  river

banks  and  buildings  the  passing  surge

might inflict; and variations in the ampli­

tude of the seismic waves, as the amount of

attenuating  rock  between  source  and  the

seismometer changed, made it possible to

estimate  the  speed  with  which  the  water

mass was travelling downriver. 

That is 20:20 hindsight, for no means of

processing the relevant data were in place

at  the  time.  But  Dr  Dietze  reckons  a  pur­

pose­built  system,  using  three  seismo­

graphic stations out of reach of the raging

waters,  could  have  done  this  and  more—

for  having  several  scattered  instruments

would also allow a flood’s front to be locat­

ed and tracked. It would permit, too, a fair

assessment  of  the  amount  of  water  in  the

bulge behind that front to be calculated.

If  this  multi­instrument  arrangement

had been in place last July it could have giv­

en the town worst affected, Bad Neuenahr­

Ahrweiler (pictured), 30­45 minutes of no­

tice before the flood arrived, and also an es­

timate of its peak level. At about €3,000 per

instrument, this would probably be a good

investment for the future in the Ahr valley,

and is also worth considering elsewhere.

Dr  Dietze  estimates  that  20%  of  Eu­

rope’s  surface  consists  of  the  kind  of  up­

land terrain which abounds with confined,

flood­prone  valleys  like  that  of  the  Ahr.

About half of this (mostly in the Alps) is al­

ready  well  served  by  flood­warning  sys­

tems. But much of the rest is hardly moni­

tored  at  all.  Scattering  a  few  cheap  seis­

mometers around theseneglected regions

might make all the differencenext time the

local weather misbehaves.n

A better way to warn of flash floods

Forewarned is forearmed

M

usicisgoodforthehealth.And

drumming may be best of all. As

well as being physically demanding, it

requires people to synchronise their

limbs and to react to outside stimuli,

such as what the rest of the band is up to. 

It is particularly helpful for children

who have emotional and behavioural

difficulties. Researchers at the Clem

Burke Drumming Project—an organisa­

tion named after Blondie’s drummer,

who was one of its founders—have

shown that teaching such children to

drum helps them to control their re­

actions more generally, to focus more

effectively on tasks they are given, and to

communicate better with other people. 

The project’s latest work, published in

the Proceedings of the National Academy of

Sciencesby a team led by Marie­Stéphanie

Cahart of King’s College, London, goes a

step further. It looks at the neurological

changes which accompany these shifts.

Ms Cahart and her colleagues recruit­

ed 36 autistic teenagers and split them

into two groups. One lot had drum les­

sons twice a week for eight weeks. The

othersdidnot.Atthebeginningandend

of the project everyone was asked to stay

still for 45 minutes in a functional mag­

netic­resonance imaging (fmri) mach­

ine, to see how the activity of their brains

had changed. Their behaviour, as report­

ed by their guardians, was also recorded.

As expected, most of the drumming

group showed positive behavioural

changes. And these were indeed reflected

in their brains. The fmriscans showed

that several clusters of connectivity

between parts of those brains had

strengthened during the experiment. In

particular, two regions involved in atten­

tion control, the right dorsolateral pre­

frontal cortex and the right inferior

frontal gyrus, formed strong links, re­

spectively, with places associated with

introspection and with areas involved in

deciphering facial expressions. 

These changes in the brain’s “wet­

ware” thus nicely match the changes in

behaviour which learning to drum in­

duces. Not a surprise, perhaps. But a

gratifying confirmation of drumming’s

power to heal.

Musictherapy

A drum, a drum, Clem Burke doth come

Learning drumming can help teenagers with behavioural problems