Atla s 14 nviro nme nta l Co mmissio n RST July 18, 2018 UNDE E - - PDF document
OOD RISK L INS F ANDING AUST Atla s 14 nviro nme nta l Co mmissio n RST July 18, 2018 UNDE E Ove rvie w 2 Ra infa ll Da ta Cha ng e s So lutio n Optio ns Re c o mme nde d Co de Ame ndme nts I mpa c ts to Re side nts
UNDE RST ANDING AUST IN’S F L OOD RISK
E nviro nme nta l Co mmissio n July 18, 2018
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Na tio nwide study
Pa rtne rs:
F
e de ra l: Na tio na l
We a the r Se rvic e , U. S. Army Co rps o f E ng ine e rs, F e de ra l Hig hwa y Administra tio n
Sta te / L
xDOT , Ha rris Co unty F lo o d Co ntro l Distric t, City o f Austin, e t a l.
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Re c urre nc e Inte rva l Curre nt Ra infa ll De pth in inc he s Atla s 14 Ra infa ll in inc he s 25- ye a r 7.6 Almost 10 100- ye a r 10.2 Up to 13+ 500- ye a r 13.5 Not ye t a va ila ble
Are a Curre nt 100- Ye a r Curre nt 500- Ye a r Diffe re nc e % Inc re a se
City L imits 3,702 6,533 2,831 76%
Are a Curre nt 100- Ye a r Curre nt 500- Ye a r % L a rg e r
City L imits 7% 9% 26%
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Appro xima te numbe r of building s in floodpla in (e xc luding Co lo ra do
Rive r flo o dpla in)
Appro xima te pe rc e nt of a re a in the floodpla in (e xc luding Co lo ra do
Rive r flo o dpla in)
Disre g a rd Atla s 14 a nd ma inta in c urre nt
Do e sn’ t pro te c t re side nts fro m flo o d
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Wa it to c ha ng e re g s until flo o dpla in studie s a re
Upda ting flo o dpla in studie s will ta ke a
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WPD will initia te flo o dpla in study upda te s
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Pro vide s imme dia te pro te c tio n a nd vita l
Use s re a dily a va ila b le , va lid da ta
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Re c urre nc e Inte rva l Curre nt Ra infa ll De pth in inc he s Atla s 14 25- ye a r 7.6 Almost 10 inc he s 100- ye a r 10.2 Up to 13+ inc he s 500- ye a r 13.5 Not ye t a va ila ble
100- ye a r =
Atla s 14 100-ye a r
E MA 500-ye a r
25- ye a r =
Atla s 14 25-ye a r o r fully de ve lo pe d 100-ye a r
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L ittle Wa lnut Cre e k Onion Cre e k
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Must sa tisfy
flo o dpla in rule s
Ac c e ss pa th min.
1-ft a b o ve
Min. 2-ft a b o ve
Ma inta in c urre nt
100-ye a r flo o dpla in a lo ng Co lo ra do Rive r
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Atla s 14 c ha ng e s no t
e xpe c te d to sig nific a ntly a ffe c t Co lo ra do Rive r wa te rshe d upstre a m o f Austin
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Colora do Rive r wa te rshe d
A re side ntia l b uilding in the 25- o r 100-ye a r
Ab o ve 100-ye a r flo o dpla in b y 2 fe e t A ma ximum g ro ss flo o r a re a tha t is the la rg e r
Do e s no t inc re a se numb e r o f dwe lling units
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Unde r c urre nt rule s: Pro pe rtie s in g re e n like ly to re de ve lo p unde r the pre -1983 e xc e ptio n Pro pe rtie s in ye llo w like ly to re de ve lo p with a n a dministra tive va ria nc e Pro pe rtie s in re d re q uire a Co unc il va ria nc e to re de ve lo p
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100- ye a r floodpla in 25- ye a r floodpla in
18 Unde r ne w rule s: All pro pe rtie s ha ve sa me
with a size limita tio n a nd e le va te d finishe d flo o r unde r a n e xc e ptio n F lo o d risk will b e re duc e d in a ll c a se s
100- ye a r floodpla in 25- ye a r floodpla in
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E
xpa nd 100-ye a r
e nc ro a c hme nt e xc e ptio n to inc lude L a ke Austin a nd L a ke T ra vis
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Co lo ra do Rive r
flo o ding is no t e xpe c te d to ha ppe n in a “fla sh”
Still re q uire s no
a dve rse impa c t a nd fre e b o a rd – wa ive s sa fe a c c e ss
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Minimum he ig ht
b e twe e n b uilding ’ s lo we st flo o r a nd 100- ye a r flo o dpla in
Mo re tha n 140 T
e xa s c o mmunitie s ha ve fre e b o a rd o f 2 fe e t o r hig he r
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F
re e b o a rd is the sing le -mo st e ffe c tive me a ns fo r re duc ing flo o d risk to a b uilding in the flo o dpla in
Simplify c o de – c urre nt fre e b o a rd re q uire me nt fo r
a dministra tive flo o dpla in va ria nc e s a nd Ce ntra l Busine ss Are a e xc e ptio n is 2 fe e t, e lse whe re it’ s 1 fo o t
Re duc e d flo o d insura nc e c o sts c a n o ffse t inc re a se d
c o nstruc tio n c o st
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Ra te s ma y g o up I
nsura nc e re q uire me nts ma y c ha ng e
T
a lk to a n insura nc e a g e nt no w
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Pla nning Co mmissio n Pla nning Co mmissio n Pub lic He a ring Ordina nc e Ado ptio n C&O Co mmitte e (PC & ZAP) E nviro nme nta l Co mmissio n Pub lic He a ring City Co unc il Pub lic He a ring I nte rna l a nd E xte rna l Sta ke ho lde r Me e ting s
3 pub lic he a ring s
At le a st 4 sta ke ho lde r me e ting s
C&O Co mmitte e (PC & ZAP) July I nte rna l a nd E xte rna l Sta ke ho lde r Me e ting s July DI F M Co mmitte e (E nviro nme nta l Co mmissio n) July June July Aug ust Aug ust Aug ust Oc to b e r Pub lic E duc a tio n & Outre a c h
Pub lic He a ring s & Sta ke ho lde r Me e ting s
Che c k AustinT
e xa s.g ov/ a tla s14 fo r de ta ils
Pub lic E
duc a tio n & Outre a c h
Po st c a rds to pro pe rtie s in 100/ 500-ye a r flo o dpla ins Ge o g ra phic a lly b a se d pub lic me e ting s
WPD sta ff to de te rmine a pplic a tio n o f ra infa ll va lue s
fo r Austin a re a (Oc t-De c 2018)
Rule s c ha ng e pro c e ss – DCM (Q2 o r Q3 o f F
Y 2019)
Re -ma pping o f Austin flo o dpla ins (2019 – 2021)
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10.1 12.5 10.2 13.2
8 9 10 11 12 13 14 1960 1970 1980 1990 2000 2010 2020
Ra infa ll De pth (inc he s) Ye a r Study Pub lishe d
Ra infa ll fro m 100-ye a r 24 hr sto rm
T P- 40, 1961 Austin DCM, 1977 USGS, 1998 Atla s 14, 2018
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200 400 600 800 1,000 1,200 1,400 1940 1950 1960 1970 1980 1990 2000 2010
Numbe r of Struc ture s
De c a de Built
Count of structures in the current 100‐year floodplain by decade
1983: Regulations
introduced to prevent encroachment into the 100‐ year floodplain
2,000 4,000 6,000 8,000 10,000 12,000 14,000 1940 1950 1960 1970 1980 1990 2000 2010 2020
Cumula tive No. Struc ture s in F loodpla in
De c a de Built
Count of structures in the current 100‐year floodplain by decade Hypothetical number of structures in floodplains without regulatory protections
12,000
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